Load scripts and styles via ResourceLoader

A base class of ResourceLoaderGlobalModule is created,
which extends ResourceLoaderWikiModule.

* ResourceLoaderGlobalUserModule is used for enabling
  User:$username/global.js and User:$username/global.css.
* ResourceLoaderGlobalSiteModule is used for enabling
  MediaWiki:Global.js and MediaWiki:Global.css.

Bug: 57225
Bug: 57224
Change-Id: I9329573da7d4f2af60515ef32b3b64bb769e3755
Merge "Load scripts and styles via ResourceLoader"