VENOM-361: Distribute avatar

[naxuroqa]

• Add a file chooser for avatars
• Set avatar resolution to 128x128
• Add a filter for images to filechooser
• Add callbacks to ToxAdapterSelfListener
• Fix tox avatars directory position
• Fix bug in FileTransferListener preventing user from sending files
• Rework user_info_widget, add avatars from /usr/share/pixmaps/faces
• Send avatar to all online contacts immediately
• Send to offline contacts when they come online

closes #361

[codecov-io]

Codecov Report

Merging #364 into develop will decrease coverage by 16.99%.
The diff coverage is 2.59%.

@@            Coverage Diff             @@
##           develop     #364     +/-   ##
==========================================
- Coverage    37.69%   20.69%    -17%     
==========================================
  Files           49       90     +41     
  Lines         2876     5237   +2361     
==========================================
  Hits          1084     1084             
- Misses        1792     4153   +2361

Impacted Files	Coverage Δ
src/core/UserInfo.vala	0% <0%> (ø)
src/core/FileTransfer.vala	4.8% <0%> (-0.35%)	⬇️
src/viewmodel/UserInfoViewModel.vala	0% <0%> (ø)
src/view/ApplicationWindow.vala	0% <0%> (ø)
src/tox/ToxContact.vala	72.72% <0%> (ø)	⬆️
src/tox/ToxAdapterFriendListener.vala	0% <0%> (ø)
src/view/UserInfoWidget.vala	0% <0%> (ø)
src/viewmodel/FriendInfoViewModel.vala	0% <0%> (ø)
src/viewmodel/ContactListViewModel.vala	0% <0%> (ø)
src/tox/ToxAdapterSelfListener.vala	0% <0%> (ø)
... and 49 more

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