JSDuck-ify /resources/mediawiki/mediawiki.Uri.js

JSDuck-ify /resources/mediawiki/mediawiki.Uri.js

* Cleaned up the whole-class documentation block.
* Marked some methods which looked internal as @private.
* Added or fixed some @return types.
* Documented instance properties.
* Fixed format of doc comments to conform to JSDuck standards,
  wrapped comments to 100 characters.
* Did some spelling and grammar fixes.
* Added entries to categories.json and config.json.

Also simplified and commented some code in #parse.

Change-Id: I0159282ef56e55f9d19f45d9e80e00c3c89eaa25