R1:25965260c431

Add a rough "!history" email command to get an entire object history via email

Summary:
See PHI505. Ref T13124. If you're an agent of a hostile state trying to exfiltrate corporate secrets, you might find yourself foiled if Phabricator is secured behind a VPN.

To assist users in this situation, provide a "!history" command which will dump the entire history of an object in a nice text format and get through the troublesome VPN.

Some issues with this:

- You currently get all the "X added a comment."…