R1:88e7cd158f28

Allow Spaces to be archived

Summary:
Ref T8377. This adds a standard disable/enable feature to Spaces, with a couple of twists:

- You can't create new stuff in an archived space, and you can't move stuff into an archived space.
- We don't show results from an archived space by default in ApplicationSearch queries. You can still find these objects if you explicitly search for "Spaces: <the archived space>".

So this is a "put it in a box in the attic" sort of operation, but that seems fairly…