Add support for patched talkgroups

[natecarlson]

Modern trunk-recorder versions include the patched_talkgroups attribute within a call.

It would bre awesome to extend OpenMHz to support this (would also need to update the openmhz_uploader plugin in trunk-recorder), and include the call in both talkgroups.

If the current model can't easily be extended to allow a single call to exist in both TGs, could also create a copy of it in each TG.. but that would result in duplicate calls if the end user has both TGs selected.