Introducing a Scopes Mapper to map from RA scopes to TextMate scopes with fallbacks.

Current scopes defined:
```
    ['keyword.unsafe', ['storage.modifier', 'keyword.other', 'keyword.control']],
    ['function', ['entity.name.function']],
    ['parameter', ['variable.parameter']],
    ['type', ['entity.name.type']],
    ['builtin', ['variable.language', 'support.type', 'support.type']],
    ['text', ['string', 'string.quoted', 'string.regexp']],
    ['attribute', ['keyword']],
    ['literal', ['string', 'string.quoted', 'string.regexp']],
    ['macro', ['support.other']],
    ['variable.mut', ['variable']],
    ['field', ['variable.object.property']],
    ['module', ['entity.name.section']]
```

Need to complement with further fallbacks as some themes fail.

editors/code/src/config.ts

@@ -1,5 +1,6 @@
 import * as vscode from 'vscode';
 import * as scopes from './scopes';
+import * as scopesMapper from './scopes_mapper';
 import { Server } from './server';
 
 const RA_LSP_DEBUG = process.env.__RA_LSP_SERVER_DEBUG;
@@ -49,6 +50,7 @@ export class Config {
         
         Server.highlighter.removeHighlights();
         scopes.load()
+        scopesMapper.load()
         if (config.has('highlightingOn')) {
 
             this.highlightingOn = config.get('highlightingOn') as boolean;