Deprecate AET maven plugin

[malaskowski]

Description

Since AET have its WebAPI for running suite, maven plugin is no longer required.

Motivation and Context

There are many problems with maven-plugin, e.g. it version changes and it might be misleading if you are using plugin version e.g. 2.1.1 does that mean you run suite on AET 2.1.1 or newer.
AET have its WebAPI to schedule running suites and since maven plugin only proxies as HttpClient, supporting it and releasing is no longer necessary. AET client script should be used instead (or simply communicate with AET Web API to schedule your suite).
Additionally I've updated missing documentation about AET WebEndpoints (like /suite, /suitestatus and /xunti).

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

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I hereby agree to the terms of the AET Contributor License Agreement.