If the contact doesn't have an image, render a color-coded
background and the first letter of the contact's name.
1) Don't display anything during recipient resolution.
2) Display a # icon in material gray for recipients with no name.
3) Display a material group icon in material gray for groups with
no avatar icon set.
Closes#3104
// FREEBIE
1) Switch to new TextSecureAddress addressing, rather than mixing
long-based recipient IDs into libtextsecure.
2) Get rid of RecipientFormattingException throws in calls to
RecipientFactory.
Closes#2570
1) When registering with server, indicate that the server should
store messages and send notifications.
2) Process notification GCM messages, and connect to the server
to retrieve actual message content.
