Support for SignalK JSON

[ktuukkan]

Signalk support would ideally provide translation from NMEA direct to signalk, and potentially in reverse, although this is more complex as you generally need a variety of signalk data values for a single NMEA message.

[ktuukkan]

NMEA to a map of SignalK values: https://github.com/SignalK/signalk-core-java/blob/master/src/main/java/nz/co/fortytwo/signalk/handler/NMEAHandler.java

Associated tests: https://github.com/SignalK/signalk-core-java/blob/master/src/test/java/nz/co/fortytwo/signalk/handler/NMEAHandlerTest.java