[Zeppelin 546](documentation) Enables interpreter library loading from maven repository

docs/_includes/themes/zeppelin/_navigation.html

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               <a href="#" data-toggle="dropdown" class="dropdown-toggle">Interpreter <b class="caret"></b></a>
               <ul class="dropdown-menu">
                 <li><a href="{{BASE_PATH}}/manual/interpreters.html">Overview</a></li>
+                <li><a href="{{BASE_PATH}}/manual/dynamicinterpreterload.html">Dynamic Interpreter Loading</a></li>
                 <li role="separator" class="divider"></li>
                 <li><a href="{{BASE_PATH}}/interpreter/cassandra.html">Cassandra</a></li>
                 <li><a href="{{BASE_PATH}}/interpreter/elasticsearch.html">Elasticsearch</a></li>

docs/manual/dynamicinterpreterload.md

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+---
+layout: page
+title: "Dynamic Interpreter Loading"
+description: ""
+group: manual
+---
+<!--
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+{% include JB/setup %}
+
+## Dynamic Interpreter Loading using REST API
+
+Zeppelin provides pluggable interpreter architecture which results in a wide and variety of the supported backend system. In this section, we will introduce **Dynamic interpreter loading** using **REST API**. This concept actually comes from [Zeppelin Helium Proposal](https://cwiki.apache.org/confluence/display/ZEPPELIN/Helium+proposal).
+Before we start, if you are not familiar with the concept of **Zeppelin interpreter**, you can check out [Overview of Zeppelin interpreter](../manual/interpreters.html) first.
+
+<br/>
+## Overview 
+In the past, Zeppelin was loading interpreter binaries from `/interpreter/[interpreter_name]` directory. They were configured by `zeppelin.interpreters` property in `conf/zeppelin-site.xml` or `ZEPPELIN_INTERPRETERS` env variables in `conf/zeppelin-env.sh`. They were loaded on Zeppelin server startup and stayed alive until the server was stopped.
+In order to simplify using 3rd party interpreters, we changed this way to **dynamically** load interpreters from **Maven Repository** using **REST API**. Hopefully, the picture below will help you to understand the process. 
+<center><img src="../assets/themes/zeppelin/img/docs-img/zeppelin_user.png" height="85%" width="85%"></center>
+
+## Load & Unload Interpreters Using REST API
+
+### 1. Load 
+You can **load** interpreters located in Maven repository using REST API, like this:
+
+( Maybe, you are unfamiliar with `[interpreter_group_name]` or `[interpreter_name]`. If so, please checkout [Interpreters in Zeppelin](../manual/interpreter.html) again. )
+
+```
+http://[zeppelin-server]:[zeppelin-port]/api/interpreter/load/[interpreter_group_name]/[interpreter_name]
+```
+The Restful method will be <code>**POST**</code>. And the parameters you need are:
+
+  1.  **Artifact:** Maven artifact ( groupId:artifactId:version ) 
+
+  2.  **Class Name:** Package name + Interpreter class name
+
+  3. **Repository ( optional ):** Additional maven repository address
+
+For example, if you want to load `markdown` interpreter to your Zeppelin, the parameters and URL you need may look like:
+
+```
+http://127.0.0.1:8080/api/interpreter/load/md/markdown
+```
+
+```
+{
+  "artifact": "org.apache.zeppelin:zeppelin-markdown:0.6.0-incubating-SNAPSHOT",
+  "className": "org.apache.zeppelin.markdown.Markdown",
+  "repository": {
+    "url": "http://dl.bintray.com/spark-packages/maven",
+    "snapshot": false
+  }
+}
+```
+
+
+The meaning of each parameters is: 
+
+  1. **Artifact**
+	- groupId: org.apache.zeppelin
+	- artifactId: zeppelin-markdown
+	- version: 0.6.0-incubating-SNAPSHOT
+
+  2. **Class Name**
+	- Package Name: org.apache.zeppelin
+	- Interpreter Class Name: markdown.Markdown
+
+  3. **Repository ( optional )**
+	- Url: http://dl.bintray.com/spark-packages/maven
+	- Snapshot: false
+
+> <b>Please note: </b>The interpreters you downloaded need to be **reload**, when your Zeppelin server is down. 
+
+### 2. Unload
+If you want to **unload** the interpreters using REST API, 
+
+```
+http://[zeppelin-server]:[zeppelin-port]/api/interpreter/unload/[interpreter_group_name]/[interpreter_name]
+```
+In this case, the Restful method will be <code>**DELETE**</code>.
+
+<br/>
+## What is the next step after Loading ?
+
+### Q1. Where is the location of interpreters you downloaded ?
+
+Actually, the answer about this question is in the above picture. Once the REST API is called, the `.jar` files of interpreters you get are saved under `ZEPPELIN_HOME/local-repo` first. Then, they will be copied to `ZEPPELIN_HOME/interpreter` directory. So, please checkout your `ZEPPELIN_HOME/interpreter`.
+
+### Q2. Then, how can I use this interpreter ?
+
+After loading an interpreter, you can use it by creating and configuring it in Zeppelin's **Interpreter tab**.
+
+Oh, you don't need to restart your Zeppelin server. Because it is **Dynamic Loading**, you can configure and load it **at runtime** !
+
+1. After Zeppelin server up, browse Zeppelin home and click **Interpreter tab**.
+<center><img src="../assets/themes/zeppelin/img/docs-img/interpreter_setting_1.png" height="85%" width="85%"></center>
+
+2. At the **Interpreter** section, click **+Create** button. 
+<center><img src="../assets/themes/zeppelin/img/docs-img/interpreter_setting_2.png" height="85%" width="85%"></center>
+
+3. Then, you can verify the interpreter list that you loaded.
+<center><img src="../assets/themes/zeppelin/img/docs-img/interpreter_setting_3.png" height="85%" width="85%"></center>
+
+4. After choosing an interpreter, you can configure and use it. Don't forget to save it.
+
+5. Create a new notebook in the **Notebook** section, then you can bind the interpreters from your interpreter list. Just drag and drop !
+<center><img src="../assets/themes/zeppelin/img/docs-img/interpreter_binding_1.png" height="85%" width="85%"></center>
+<center><img src="../assets/themes/zeppelin/img/docs-img/interpreter_binding_2.png" height="85%" width="85%"></center>
+
+6. At last, you can use your interpreter !
+
+If you want to get the specific information about respective interpreters, please checkout each interpreter documentation.