#114 Allow saving of a constructed BACnet service

[cg_mayoor]

Considering the fact that VTS crashes innumerable times, a feature for saving and storing a constructed BACnet service will be of paramount help. The feature should enable a user to open a saved BACnet service and then modify, edit and use(send) it in the BACnet network.

Reason for this demand:
1. As said above, VTS crashing induces rework of BACnet service generation.
2. Lot of BACnet services generated in a single session will be lost when either VTS application is closed or PC is shut down( or restarted), etc.
3. There are multiple occasions where a VTS user will have to switch from/to VTS to/from some other BACnet client tool. During these transitions, precious effort in construction of BACnet services get wiped out.

This is a request. Please consider.