Do not create folders on readonly repositories

1) Rename the unintuitive repository.syncfoldersto() to
sync_folder_structure()

2) We were checking if the local repository is readonly and then turning
off any folder creation. But as we can create folders on a remote
repository too, we need to be more fine grained here. Just don't create
a folder on the repository that is marked readonly=True.

This still does not do away with the error message that one currently
gets on missing local folders.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

offlineimap/accounts.py

@@ -289,10 +289,10 @@ class SyncableAccount(Account):
             localrepos.getfolders()
             statusrepos.getfolders()
 
+            remoterepos.sync_folder_structure(localrepos, statusrepos)
             # replicate the folderstructure between REMOTE to LOCAL
             if not localrepos.getconfboolean('readonly', False):
                 self.ui.syncfolders(remoterepos, localrepos)
-                remoterepos.syncfoldersto(localrepos, statusrepos)
 
             # iterate through all folders on the remote repo and sync
             for remotefolder in remoterepos.getfolders():