Support for simultaneous GPS and Spektrum satellite and Spektrum satellite binding.

I have created couple of improvements:
- Possibility to use Spektrum satellite and GPS simultaneous. It's done by using softserial on GPS.
- 8 channel support for DSMX.
- Possibility to bind Spektrum satellite with TX without using separate RX for binding.
there is digitalLo/digitalHi macros in board.h for this, not to pull dependency on gpio_stm32f103.c