Make IDLE_TIMEOUT avoidable with account-lock.

Resolves #701. Check the Account-lock 'no_idle_disconnect before kicking an idle
session. This also means superusers will never be kicked. Move the
idle task to the Server to avoid lock imports in Portal. Make the
'lock' command also able to target Accounts. Also some other fixes.

evennia/server/portal/telnet.py

@@ -116,6 +116,12 @@ class TelnetProtocol(Telnet, StatefulTelnetProtocol, Session):
                 # do the sync
                 self.sessionhandler.sync(self)
 
+    def at_login(self):
+        """
+        Called when this session gets authenticated by the server.
+        """
+        pass
+
     def enableRemote(self, option):
         """
         This sets up the remote-activated options we allow for this protocol.