Add options to include patches inline or attached for Diffusion commit emails

Summary:
See D818 for an older attempt at this. Support code has matured to the point where the patch is pretty straightforward.

@tido, this was a long-standing request from Aditya back in the day.

Test Plan: Used reparse.php --herald to send myself a bunch of emails with various patch configurations. Confirmed that limits are respected, reasonable errors arise when they're violated, etc. (Timeout is a little funky but that's out of scope here, I think.)

Reviewers: btrahan

Reviewed By: btrahan

CC: tido, aran

Maniphest Tasks: T456

Differential Revision: https://secure.phabricator.com/D2967