Add a synapse.lib.storm.Cmd class to the cortex.

def addStormCmd(self, ctor):
        '''
        Add a synapse.lib.storm.Cmd class to the cortex.
        '''
        if not s_syntax.isCmdName(ctor.name):
            raise s_exc.BadCmdName(name=ctor.name)

        self.stormcmds[ctor.name] = ctor