R1:13cac5c362bb

Add Spaces to Projects

Summary:
See PHI774. Ref T13164. There is no reason projects //don't// support Spaces, just a vague concern that it's not hugely useful and might be a bit confusing.

However, it's at least somewhat useful (to improve consistency and reduce special casing) and doesn't necessarily seem more confusing than Projects are anyway. Support is trivial from a technical point of view, so just hook it up.

Test Plan: Created new projects, shifted projects between spaces. The support is all…