FrSky telemetry update
Add MSP_API_VERSION command.  Added MSP development guidelines.  Define
board identifiers for all cleanflight targets.
Fix a couple of typos in MSP guidelines.
Merge branch 'airmamaf' of github.com:airmamaf/cleanflight into airmamaf-airmamaf
Merge branch 'airmamaf-airmamaf'
Clean up pull request #108 from @Airmamaf.
Updating FrSky telemetry docs to match recent code changes.
Updating credits for FrSky telemetry.
Bump EEPROM version (for #108).
Updating serial port details for Naze board.
Latest binaries with FrSky telemetry updates and first cut of
MSP_API_VERSION command.
Fixed bug where channel mapping was incorrect when using GPS and RX
Parallel PWM on STM32F10X targets. Fixes #80.

The check to see if usart2 should always be done.  The PWM mapping code
decides on a per-target base if possible pwm input channels need to be
skipped due to pin usage clashes.
SoftSerial port for CC3D
Merge pull request #124 from Pierre-A/cc3d-updates-1

SoftSerial port for CC3D
Undo changes from 20c4dae7c27eec6f31475fb65596b3fa3aa5f67b / hott.c
until a proper fix is found.
Cleanup CC3D softserial - it only has enough pins/timers for one port.
PR #124 incorrectly re-used the same timer hardware for the second port
which was bad.
Fix opening softserial ports - missed a #ifdef check.
Cleanup Softserial/LedStrip timer clash checking.  Move definitions of
led strip timer and softserial pwm ports/timers into target specific
files.
Workaround for HoTT and softserial.
Use correct buffer size variable when checking for softserial waiting
bytes.  Fixes #127.