Version 0.3.9

Version 0.3.9

Changelog:

- NMEA
  - field parsing separated to its own file, unit tests added.
  - refactoring of hemisphere conversion/correction.
  - sntences API change for interpreting fields, collected from raw sentences.

- Geo:
  - minor cleanup of angle, some constexpr.

- Doc:
  - enhancements, information about benchmarking.

- Build:
  - AIS is now optional, use flag 'ENABLE_AIS'.
  - SeaTalk is now optional, use flag 'ENABLE_SEATALK'.

- Dev:
  - added build option and documentation regarding optimization and benchmarking.
  - added script to extract changelog between version tags.
  - infrastructure for benchmarking, NMEA: parse_fields improved.
  - script to extract changelog extended.