- added Msg frame work with Msg container , Msg sources, Msg sinks

- added filter by message type to nmea receiver
- show case new features in MultiClient.main()

msg_source.py

@@ -0,0 +1,15 @@
+from abc import ABC
+from msg_montainer import MsgContainer
+from msg_sink import MsgSink
+
+class MsgSource(ABC):
+	def __init__(self):
+		self.sinks = {}
+
+	def register_recv(self, name: str, sink: MsgSink):
+		self.sinks[name] = {'sink': sink}
+
+	def call_sinks(self, msg: MsgContainer):
+		if msg.name in self.sinks:
+			sink = self.sinks[msg.name]['sink']
+			sink.on_recv(msg)