logging: '-V' cli option can blacklist/whitelist classes with short names

for example, '-V ni' will whitelist the 'Network' and 'Interface' classes
'-V ^ni' will blacklist those instead

electrum/util.py

@@ -260,6 +260,8 @@ class DebugMem(ThreadJob):
 class DaemonThread(threading.Thread, Logger):
     """ daemon thread that terminates cleanly """
 
+    LOGGING_SHORTCUT = 'd'
+
     def __init__(self):
         threading.Thread.__init__(self)
         Logger.__init__(self)