* Changed OutputPage::$mIsArticle flag to be false by default. A lot of actions don...

* Changed OutputPage::$mIsArticle flag to be false by default. A lot of actions don't change that flag when they should, since about only action=view should have it to true.
* Put OutputPage::$mIsArticleRelated declaration just below $mIsArticle's one since they are related
* Made DifferenceEngine consistent with action=view, i.e. setting that flag to true when displaying any version of the page, current or not
* Made Skin::getCopyright() always use history_copyright when displaying an old version, regardless to the diff parameter
* Changed some checks from namespace != NS_SPECIAL && action=view to isArticle() so that they don't get executed when e.g. throwing an Exception (or similar things)