handle a new target_system

def add_new_target_system(self, sysid):
        '''handle a new target_system'''
        if sysid in self.pstate:
            return
        if not sysid in self.mpstate.mav_param_by_sysid:
            self.mpstate.mav_param_by_sysid[sysid] = mavparm.MAVParmDict()
            self.new_sysid_timestamp = time.time()
        fname = 'mav.parm'
        if sysid not in [(0,0),(1,1),(1,0)]:

            fname = 'mav_%u_%u.parm' % (sysid[0], sysid[1])
        self.pstate[sysid] = ParamState(self.mpstate.mav_param_by_sysid[sysid], self.logdir, self.vehicle_name, fname)
        if self.continue_mode and self.logdir is not None:
            parmfile = os.path.join(self.logdir, fname)
            if os.path.exists(parmfile):
                mpstate.mav_param.load(parmfile)
                self.pstate[sysid].mav_param_set = set(self.mav_param.keys())
        self.pstate[sysid].xml_filepath = self.xml_filepath