Refactor/mstp zero config state machine (#676)

* Changed MS/TP master node self destination checks to be located in receive FSM

* Changed MSTP zero configuration: modified comments for state transition names; modified next station increment; refactored the UUID rand() to not be required by common zero config implementation; added more unit tests.

* Added another context to MS/TP user data to allow additional user data

src/bacnet/datalink/dlmstp.h

@@ -97,7 +97,7 @@ struct dlmstp_rs485_driver {
 };
 
 /**
- * A structure of BACnet Port Data for BACnet MS/TP
+ * An example structure of user data for BACnet MS/TP
  */
 struct dlmstp_user_data_t {
     struct dlmstp_statistics Statistics;
@@ -107,6 +107,7 @@ struct dlmstp_user_data_t {
     struct dlmstp_packet PDU_Buffer[DLMSTP_MAX_INFO_FRAMES];
     bool Initialized;
     bool ReceivePacketPending;
+    void *Context;
 };
 
 /* callback to signify the receipt of a preamble */