Support v3.x DDN Firmware

DDN changed the format for the latency data in their 3.x firmware. This release includes code to handle that change.

A few notes regarding the changes:

• The change to support v3.x firmwares requires changes to the SQL database schema (and InfluxDB fields, if you're using InfluxDB), so make sure you specify the -i parameter to initialize the database(s) the first time DDNTool is started after the firmware update.
• One instance of DDNTool can support DDN's with either 3.x or 2.x firmware, but don't try to use the same instance to connect to DDN's running mixed versions.