View source for Proposals/Combine pages and collections

Combine pages and collections so they show up together in order to make it easier for people to find where they are and not go to two different places for updating their pages.

[[Media:Pages_collections_201702.pdf | Mock-ups for the 2017 implementation]].

* The colours and styling of the boxes has not yet been finalised.
* The "Create" and "Copy" buttons stay where they are (mock-up hasn't been updated to reflect that) so that we get an even number of boxes for the pages and collections.
* Page icon on collection box may change slightly.