Ref T3657. General changes here:
- Removes ReleephProjectController, which is the source of T3657.
- Mostly moves requests from "RQ" as a monogram to "Y" (looks like a merge, mnemonic for "yank"?, we don't have too many characters left). This should be essentially only cosmetic. This reduces ambiguity with "rQ" and "R123", which are current and future repository monograms. This will continue in the next few diffs.
- Makes requests implement policies correctly.