R1:2fd018ad92c5

Begin transacitonalizing repository edits and provide a more sensible edit interface

Summary:
Ref T2231, T603. Plan of attack here is pretty much:

- Built out a new (currently not linked in the UI) edit interface in Diffusion which is transaction-based and has a sensible layout.
- Build out a new create interface based on PagedForm which dumps into the new edit interface.
- Throw the old stuff away.
- Everyone lives happily ever after.

Test Plan:
{F44163}
{F44164}

Reviewers: chad, btrahan…