* Moved post-deletion code from WikiPage::doDeleteArticle() to WikiPage::doDeleteUpda...

* Moved post-deletion code from WikiPage::doDeleteArticle() to WikiPage::doDeleteUpdates() so that it can be shared with page move
* Use WikiPage::doEditUpdates() and WikiPage::onArticleDelete() to do updates instead of reimplementing the whole thing in Title::moveTo(); avoids some bugs since the implementation differs from the one from WikiPage (notably the page and article count). This adds some more cache clearing, but they are needed depending on parameters (e.g. if the redirect is not created).