mm-account: Add mmsd Support to Chatty

These are a set of patches to add mmsd-tng based MMS Support into Chatty. Backend support is complete, and supports all MMS functionality (Sending, Receiving, Group MMS, Delivery Reports, etc). There is still some work needed to properly integrate MMS support into the UI.

These patches require version 1.1 of mmsd-tng (but 1.2 is recommended to fix a sending bug).

Rather than track remaining issues here, I added a roadmap issue here: #571 (closed)