Webmail improvements. (drap&drop of messages for moving and deleting, empty trash, etc.)

lib/__init__.py

@@ -78,3 +78,14 @@ def getoption(name, default=None):
     except AttributeError:
         res = default
     return res
+
+
+class Singleton(type):
+    def __init__(cls, name, bases, dict):
+        super(Singleton, cls).__init__(name, bases, dict)
+        cls.instance = None
+
+    def __call__(cls, *args, **kwargs):
+        if cls.instance is None:
+            cls.instance = super(Singleton, cls).__call__(*args, **kwargs)
+        return cls.instance