Add meta items for the four remaining mwPageProp behavioural flags from Parsoid
that are added by MediaWiki core. These are each waiting for UX implementation,
based on the lack of context information in MWMetaDialog about the page, or
about the wiki:
* __NOGALLERY__
* __HIDDENCAT__
— These only make sense in a Category: page.
* __NOTITLECONVERT__ // __NOTC__
* __NOCONTENTCONVERT__ // __NOCC__
— These only make sense on wikis that have content or title conversion.
Change-Id: I752705f65cfbd79c7f3f71270659793996868aff
