* Refactor Title::isValidMoveOperation() and Title::moveTo() to return an array of...

* Refactor Title::isValidMoveOperation() and Title::moveTo() to return an array of arrays like Title::getUserPermissionsErrors() does; other functions used by the write API have undergone similar refactoring earlier
* Handle these return values in MovePageForm::doSubmit() and ApiMove::execute()
* Remove separate AbortMove hook calls from MovePageForm and ApiMove; these were used to capture the hook error, but the new return type handles that. Also, it resulted in two calls to that hook for each move
* Remove comment about SpecialMovepageAfterMove hook from ApiMove::execute(): we don't need it, there's the TitleMoveComplete hook for that. SpecialMovepageAfterMove is a UI hook that doesn't belong in the API
* Add imagenocrossnamespace and imagetypemismatch errors to ApiBase::$messageMap