gae_memcache.clear(), thanks Matt

gluon/contrib/gae_memcache.py

@@ -47,10 +47,12 @@ class MemcacheClient(Client):
         self.set((time.time(), value))
         return value
 
-    def clear(self, key):
-        key = '%s/%s' % (self.request.application, key)
-        self.delete(key)
-
+    def clear(self, key = None):
+        if key:
+            key = '%s/%s' % (self.request.application, key)
+            self.delete(key)
+        else:
+            self.flush_all()