Major stability improvement for streaming mode with internal GPS:

- FEATURE_STREAM changed to bit field:
   1 = GPS location streaming
   2 = GPS track history streaming (still only on Renault Twizy)

- Concurrency between location stream msg and internal modem
  GPS request resolved by round robin style time slot usage

- Modem GPS response (and other multi line modem outputs) now parsed
  completely within one main loop cycle
Merge branch 'master' of https://github.com/markwj/Open-Vehicle-Monitoring-System.git
Version = 2.3.6 (GPS streaming fixes)