SD-175: Manually mark users as established

https://snowdrift.coop/p/snowdrift/w/moderation/c/967

Current behavior:

- A user is either unestablished, eligible for establishment, or established
- Any moderator is allowed to make users eligible for establishment. The user must read and accept the honor code to become established. A moderator can't short-circuit this process.
- A "establish user" form appears at the bottom of a user's profile (/u/#UserId) **if** the viewer is a moderator of *some* project **and** the user is unestablished.
- Establishment **requires** a reason (text field)
- When a user becomes eligible for establishment, they will receive a message from **snowdrift** congratulating them and instructing them to please read and accept the honor pledge, located at **/honor-pledge**
- An "establish user" link is added to the comment view of unmoderated comments. It links to the user's profile (redundant, but still useful - the moderator can also click the hyperlinked user's name to arrive at the same page)

What needs work:

- The "establish user" form on the user page looks awful, I didn't even try to make it look pretty (@wolftune, want this one?)
- The honor pledge HTML needs to be pulled out of the wiki and put at **/honor-pledge** (HonorPledgeR). Currently there's some dummy HTML there.