Start moving page move logic out of Title

This moves most of the Title::moveTo() function into a new MovePage
class, and the entirety of the Title::moveToInternal() function.

No actual code was changed except for requiring a User object in
function arguments instead of relying up on $wgUser, and changes
to "$this" as necessary.

Change-Id: I5479fa8f3920a51ddf789d55edae7dd0d9b24382
Merge "Start moving page move logic out of Title"