* Tweaked Revision class to handle loading the current user name instead of rev_user_...

* Tweaked Revision class to handle loading the current user name instead of rev_user_text. It still falls back to rev_user_text when building objects from DB rows for b/c.
* Moved JOIN conds to fetchFromConds() as that's where the tables are specified. This lets us avoid the same page_id=rev_page join conds plastered all over the code. Also, we can't mix WHERE and JOIN style join conds.
* Removed duplication in fetchFromConds() by using selectPageFields().
* Removed duplicate rev_parent_id field from contribs SELECT.

Yo make use of these changes, Pagers and lists still need to be updated to use Revision::selectUserFields() and join on the user table.