R1:37893ba2e632

Allow EditEngine configurations to be disabled and marked as "Default"

Summary:
Ref T9132.

Let configurations be enabled/disabled. This doesn't do much right now.

Let configurations be marked as default entries in the application "Create" menu. This makes them show up in the application in a dropdown, so you can replace the default form and/or provide several forms.

In Maniphest, we'll do this to provide a menu something like this:

- New Bug Report
- New Feature Request
- ADVANCED TASK CREATION!!