Scaffolding for Fund

Summary:
Ref T5835. This is all pretty boilerplate, and does not interact with Phortune at all yet.

You can create "Initiatives", which have a title and description, and support most of the expected infrastructure (policies, transactions, mentions, edges, appsearch, remakrup, etc).

Only notable decisions:

• Initiatives have an explicit owner. I think it's good to have a single clearly-responsible user behind an initiative.
• I think that's it?

Test Plan:

• Created an initiative.
• Edited an initiative.
• Changed application policy defaults.
• Searched for initiatives.
• Subscribed to an initiative.
• Opened/closed an initiative.
• Used I123 and {I123} in remarkup.
• Destroyed an initiative.

Reviewers: chad, btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5835

Differential Revision: https://secure.phabricator.com/D10481