Implement a way to see if a directory is synced or not in files view

[henri2h]

Add a icon in front of a directory element in the files view in order to know if this directory is in the sync list.

If the directory is synced, it should show :

- the sync is up to date - the sync is running - the sync failed

[pestotoast]

This needs a better implementation of a synchronization protocol, but here's a first try :) It shows if the sync is up to date or not.

[henri2h]

This is great, thanks !!!!