Update Alan LangDef: v2.0.0

This commit fixes some keywords issues and improves the syntax:
- kwd-ID 1: Add missing Keywords: `indirectly`, `meta`, `transitively`.
- kwd-ID 2: Add missing Prefefined Classes: `literal`, `string`.
- Add new keywords group (ID 3) and move `hero` into it (from kwd-ID 2).
For more details on these changes, see discussion with Alan develepor Thomas
Nilefalk (@thoni56) at:
    alan-if/alan-docs#15
    alan-if/alan-docs#17

langDefs/alan.lang

@@ -1,4 +1,4 @@
---[[ "alan.lang" v1.0.2 (2018/06/26) | Alan 3.0beta5 | Highlight v3.43 | Lua 5.3
+--[[ "alan.lang" v2.0.0 (2018/09/11) | Alan 3.0beta6 | Highlight v3.44 | Lua 5.3
 ********************************************************************************
 *                                                                              *
 *                          ALAN IF Syntax Definition                           *
@@ -130,36 +130,53 @@ Keywords = {
 --------------------------------------------------------------------------------
   { Id = 1,
     List = {
-      -- Keywords (121):
+      -- Keywords (124):
       "add", "after", "an", "and", "are", "article", "at", "attributes",
       "before", "between", "by", "can", "cancel", "character", "characters",
       "check", "container", "contains", "count", "current", "decrease",
       "definite", "depend", "depending", "describe", "description", "directly",
       "do", "does", "each", "else", "elsif", "empty", "end", "entered",
       "event", "every", "exclude", "exit", "extract", "first", "for", "form",
       "from", "has", "header", "here", "if", "import", "in", "include",
-      "increase", "indefinite", "initialize", "into", "is", "isa", "it",
-      "last", "limits", "list", "locate", "look", "make", "max", "mentioned",
-      "message", "min", "name", "near", "nearby", "negative", "no", "not",
-      "of", "off", "on", "only", "opaque", "option", "options", "or", "play",
-      "prompt", "pronoun", "quit", "random", "restart", "restore", "save",
-      "say", "schedule", "score", "script", "set", "show", "start", "step",
-      "stop", "strip", "style", "sum", "synonyms", "syntax", "system",
-      "taking", "the", "then", "this", "to", "transcript", "until", "use",
-      "verb", "visits", "wait", "when", "where", "with", "word", "words",
+      "increase", "indefinite", "indirectly", "initialize", "into", "is",
+      "isa", "it", "last", "limits", "list", "locate", "look", "make", "max",
+      "mentioned", "message", "meta", "min", "name", "near", "nearby",
+      "negative", "no", "not", "of", "off", "on", "only", "opaque", "option",
+      "options", "or", "play", "prompt", "pronoun", "quit", "random",
+      "restart", "restore", "save", "say", "schedule", "score", "script",
+      "set", "show", "start", "step", "stop", "strip", "style", "sum",
+      "synonyms", "syntax", "system", "taking", "the", "then", "this", "to",
+      "transcript", "transitively", "until", "use", "verb", "visits", "wait",
+      "when", "where", "with", "word", "words",
       -- Treat as keywords:
       "=>",          --> Shorthand for 'THEN'.
       ".", ",", ":"  --> These are never used as operators.
     }
   },
 --------------------------------------------------------------------------------
---                 Predefined Alan Classes and Special Entities                 
+--                           Predefined Alan Classes                            
 --------------------------------------------------------------------------------
+-- These are the seven predefined classes of the Alan language.
+-- 
+-- NOTE: Usually there is no need to syntax-highlight the predefined classes or
+--       the 'hero' instance (next keywords group) as there isn't anything
+--       special about them beside being hard-coded into the language.
+--       You can always style this group as normal text if you wish; I've
+--       created a dedicated keywords group for them in order to allow styling
+--       them if needed (for example, in documentation or tutorials it might be
+--       desirable to do so).
   { Id = 2,
     List = {
-      -- Built-in usable classes:
-      "actor", "entity", "location", "object", "thing",
-      -- Special entity for protagonist:
+      "actor", "entity", "literal", "location", "object", "string", "thing",
+    }
+  },
+--------------------------------------------------------------------------------
+--                             Predefined Instances                             
+--------------------------------------------------------------------------------
+-- The 'hero' is a special predefined actor instance, used for the protagonist.
+-- (See NOTE above!)
+  { Id = 3,
+    List = {
       "hero"
     }
   }
@@ -196,6 +213,20 @@ end
 This syntax definition abides to Semantic Versioning 2.0.0:
     http://semver.org
 --------------------------------------------------------------------------------
+v2.0.0 (2018/09/11) | Alan 3.0beta6 | Highlight v3.44
+    - BUG FIXES:
+      - Add missing keywords "meta", "indirectly" and "transitively".
+      - Add missing "literal" and "string" to the Predefined Alan classes.
+        For more details, see discussion with Alan develepor Thomas Nilefalk at:
+            https://github.com/alan-if/alan-docs/issues/15
+            https://github.com/alan-if/alan-docs/issues/17
+    - MAJOR CHANGES:
+      - Add new Keywords group and move "hero" there. This new group is for
+        "predefined instances", but its sole member is "hero", the predefined
+        actor instance representing the player. In some contexts, like tutorials
+        and documentation, it might be desirable to be able to syntax highlight
+        this special instance; in all other cases it can just be styled as
+        normal text (or non-styled) to visually hide it.
 v1.0.2 (2018/06/26) | Alan 3.0beta5 | Highlight v3.43)
     - BUG FIXES:
       - Now Quoted IDs are passed through as STANDARD text. Before, if Quoted IDs