Multisite updates and improvements

[taclane]

Building on the improvements in #846, trunk-recorder should use RFSS and Site ID as the default discriminators when multisite is enabled for P25 systems. This overcomes an issue where multiple P25 sites broadcasting the same NAC can circumvent de-duplication logic.

Prior to this, some P25 systems required manual setup using a multiSiteSystemName, and it may not have been apparent why it did not appear to be working using the default settings.

The existing "Preferred NAC" or multiSiteSystemNumber functionality has not changed, but users may additionally use a decimal RFSS/SiteID (in the form RRRRssss, e.g. 00030013) to match talkgroups to preferred sites.

The console message has been updated to better show the "WACN/RFSS-Site" match when it occurs:

Duplicate Grant - 20C: BEE00/3-13 23C: BEE00/3-14  Source: 1819332 Call: 20C State: recording

Manually defining a multisite system with multiSiteSystemNameor multiSiteSystemNumber remains unchanged, but the log message would look as below:

Duplicate Grant - 66C: CLMRN/0 67C: CLMRN/1  Source: 1849171 Call: 66C State: recording

[robotastic]

This all sort of makes sense to me... but the code looks good, let's ship it!