load waypoints from a file

def load_waypoints(self, filename):
        '''load waypoints from a file'''
        self.wploader.target_system = self.target_system
        self.wploader.target_component = self.target_component
        try:
            self.wploader.load(filename)
        except Exception as msg:
            print("Unable to load %s - %s" % (filename, msg))
            return
        print("Loaded %u waypoints from %s" % (self.wploader.count(), filename))
        self.send_all_waypoints()