This allows all the account state information to live in gui
while the sync-relevant data stays in libsync.
I also moved quotainfo to gui since it depends on the account state.
The account state is now managed mostly by the Account itself
instead of through Application. The gui can still control whether
an account is signed out or not.
* Stop the quota job from having an effect on account status
as it can sometimes take a long time to reply. See #2485 and
owncloud/core#12744.
* Instead of indirectly using the quota job, use the connection
validator to regularly ping the server with a basic PROPFIND for
'getlastmodified' on /.
This request was usually fast for users even when the quota PROPFIND
was slow.
