Correct mode behaviour joystick
dox fixes
[modules] airspeed_ets: retry after failed transaction
[paparazzi.py] Produces .md with branch description
[airframes] replace joystick subsystem by USE_JOYSTICK
[modules] dc: use state interface for utm position
[gps] refactor sendng of SVINFO
[modules] flight_benchmark: move settings into module xml file
[settings] remove some obsolete files
[modules] flight_time: move settings into module xml file
source and xml files should not be executable

closes #898
fix use of math lib in rotorcraft_cam module
remove trailing whitespaces
[simulator] use unconnected socket for FlightGear viz

So you can start FlightGear after the sim and not get Connection refused (send()) errors.
Should solve #915
[telemetry] replace old downlink macros with functions

- update messages generator
- generic device with uart support
- initial support of pprz protocol (transparant)
- fix types in downlink variables
[telemetry] cleaning downlink header
[telemetry] convert xbee to new downlink functions
[telemetry] start conversion of pprzlog transport
[telemetry] convert w5100 to new format

- actually, w5100 is only a device using pprz protocol
- compiling but not tested
- very strange manipulation of pointers in w5100_receive and
  w5100_read_data functions
- I doubt this is actually still working...
[telemetry] converting superbitrf to generic device API