LiveData: Initial implementation

Add support for live data subscription via Device::subscribeLiveData() and
Device::unsubscribeLiveData(). The live data API can be used to subscribe to
individual "signals", a full list of which can be found in LiveDataValueType.

include/icsneo/communication/message/message.h

@@ -37,6 +37,7 @@ public:
 		ComponentVersions = 0x800c,
 		SupportedFeatures = 0x800d,
 		GenericBinaryStatus = 0x800e,
+		LiveData = 0x800f,
 	};
 
 	Message(Type t) : type(t) {}