Cleanup to deletion related code:

Cleanup to deletion related code:
* Use the new 'cannotdelete-title' message for the title on error instead of "internal error"
* Don't use OutputPage::showFatalError() but add the content by "normal" methods (related to the item above)
* Don't use the $DeleteReason and $DeleteReasonList member variables in Article and FileDeleteForm but local variables since they are not used anywhere else
* Moved down some variable definitions near where they are used so that they are only set when they will actually be used
* Same for the setPageTitle() call with 'delete-confirm' message in Article::delete() that is now in Article::confirmDelete()
* Added missing "true" as fourth parameter of WikiPage::doDeleteArticle() call that was missing
* Factorised getTitle() and getUser() calls
* Salt token with array( 'delete', 'page title' )