Revert "Implement a sync now button"

Actually, after discussion with the team, we decided this button is a bad idea

This reverts commit b56fcd8ebd7f2b4094fdc4b826b84276c529601e.
Make F6 in the account config sync the selected folder, for debugging purposes

Issue #409
Ignore error 404 on DELETE

This may happen if we have stale entries in the database
Fix header name according to changes on server master.
Added a PropagateLocalRename job to do local renames.
Removed unused code from LocalRename
Fix crash when removing folder while syncing.

We need to set _thread to 0 after destoying it
Don't leak the system tray
Reset the proxy module property at every sync

This is required for the fix for #713
Since the module properties are shared in global variables shared by
every folders, removing another folder may clean the proxy settings.
So we need to restore them at every sync
Allow folder that are prefix of another
Fix syncing folder with nothing in it

Do the start after connecting, as the finish may be imediate if there
is nothing to do.
Merge remote-tracking branch 'origin/master' into account_refactoring

Conflicts:
	src/mirall/accountsettings.cpp
	src/mirall/folder.cpp