R1:7ed699660435

Provide basic infrastructure for moving PHIDs, Handles and Object Names to applications

Summary:
See discussion in T2715. Currently, PHIDs are all hard coded in the PHID application. In the long run, we need to move them out into actual applications.

A specific immediate issue is Releeph, which uses a very very old and very broken mechanism to inject PHIDs in a way that only sort of works.

Moving forward, every PHID type will be provided by a `PhabricatorPHIDType` subclass, which will manage loading it…