Set avatar from social network

[elementaryBot]

A killer feature would be checking with POA to see if we have any linked accounts with avatars and offer to get the avatar from that account.

Launchpad Details: #LP1409510 Daniel Fore - 2015-01-11 19:12:22 +0000

[danirabbit]

#178 kind of addresses this, but another option would be pulling an avatar from ActivityPub as in elementary/initial-setup#180