* Split off WikiPage class from Article, WikiFilePage class from ImagePage, and WikiC...

* Split off WikiPage class from Article, WikiFilePage class from ImagePage, and WikiCategoryPage from CategoryPage.
* WikiPage functions/fields are "magically" part of Article when accessed for b/c. Magic is kind of ugly but there are too many callers to make breaking changes atm. Some functions are just wrappers for WikiPage ones (were magic won't work).
* Added newFromID() to each WikiPage subclass (works around pre-existing inheritance problem).
* Added Page class for convenient type hinting and changed hints from Article -> Page. This lets things use WikiPage objects without getting type errors.
* Updated FlaggedPage to extend WikiPage. Worked around getOldIdFromRequest().
* Added setTimestamp() to WikiPage and moved some timestamp setting code from ParserCache to Article.
* Removed ampersands from $dbw arguments.
* @TODO: dependency inject user objects for WikiPage

The idea is to migrate things to use WikiPage, as the run-of-the-mill "new Article()" call doesn't care about $oldid and $wgRequest. After that, Article, ImagePage, and CategoryPage can be rewritten as an Action class or something sane (a Viewer class of sorts).