Introduce an *empty* debug type

This debug type will always be enabled whenever any debugging is enables
and it outputs debug messages that cannot be categorized among any of
imap, maildir (e.g. things that concern the sync logic).

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/ui/UIBase.py

@@ -25,7 +25,8 @@ from StringIO import StringIO
 from Queue import Empty
 import offlineimap
 
-debugtypes = {'imap': 'IMAP protocol debugging',
+debugtypes = {'':'Other offlineimap related sync messages',
+              'imap': 'IMAP protocol debugging',
               'maildir': 'Maildir repository debugging',
               'thread': 'Threading debugging'}