Fixing the mess that was r29539:

Fixing the mess that was r29539:
* $wgRequest shouldn't be used in functions like Article::doEdit() that are also called by API modules
* Moving code that decides whether the edit is bot out of DB logic and into UI logic: API and UI each decide indepentently from one another
* Removing $bot==='default' behavior from RecentChange::notifyEdit() and notifyNew(): nobody uses it, and it shouldn't be used anyway; whether the edit is bot should've been decided long ago