R1:7c8a875c1924

Implement custom fields in Projects

Summary:
Ref T4379. Ref T3794. Fixes T4010. This brings CustomFields to projects.

My primary goal is to get rid of the special casing around project profiles and profile editing, so all edits are ApplicationTransactions. Particularly, I want to make the "blurb/description" field a custom field which goes through builtin infrastructure.

A distant secondary goal is that this is a feature which users like/want because users like/want features.

Test Plan: Added a custom…