Clean-up after removing part of CorporatePage extension and occurrences of $wgEnableCorporatePageExt

Since we [partly removed CorporatePage](https://github.com/Wikia/app/commit/fb564947f573e39c80052389f127a5bce610a86c) and occurrences of [$wgEnableCorporatePageExt](https://github.com/Wikia/app/pull/765) we checked how it affected [wikia.com](http://www.wikia.com). I found inconsistencies between production and dev versions (except out-dated content of articles). First one was a regular page header and I brought it back by adding another "else if" block in our Oasis BodyController.

After that most of the pages looked as on production except Mobile page and its sub-pages -- there is a search form visible next to page title in header. But the content is out-dated and on production I saw the form is hidden by CSS rule in article's content.

I'm more worried about the sub-page example:
http://www.wikiaglobal.nandy.wikia-dev.com/wiki/Press (this isn't valid anymore -- code changes were done which fixed it)

At the beginning after removal of CorporatePage the right rail has the same modules within as on regural wiki. When [on production](http://www.wikia.com/Press) you can notice there is only the search. I wanted to accomplish that by creating hook in WikiaHomePage extension. It almost worked, except "Related Video" module. @saipetch @lizlux @garthwebb can I modify your code and add to the [onGetRailModuleList hook method](https://github.com/Wikia/app/blob/dev/extensions/wikia/RelatedVideos/RelatedVideos.hooks.php#L136) condition which hides the module on corporate pages?

@moliwikia @macbre @gabrys @owend @federico-lox an eye on the changes are most welcome :)