Small fixes
GTK+3 compatibility
GTK+3 compatibility. Fixes in format converter.
Fixed crashing in while populate vk tree. Fixed vk tree rendering.
Improved stability
Merge remote-tracking branch 'remotes/upstream/gtk3' into origin/gtk3

Conflicts:
	src/foobnix/util/file_utils.py [resolved]
Improved GTK+3 compatibility
Remake "Open file manager"