[types] add support for new telemetry types

Comming from the old 'messages' branch:
- support for char and 64 bytes
- support for fixed length arrays
[convert] support for ARCH_ALIGN_INT64
[messages] add char, fixed size array and int64 support to transports and gen_messages.ml
Merge pull request #589 from gautierhattenberger/pprz_type

[types] add support for new telemetry types
[baro] PRINT_CONFIG_MSG for USE_BARO_BOARD and USE_BAROMETER
[dox] some doxygen updates
add CONTRIBUTING.md
[ubx] improve ubx parser and ubx_ucenter module

- configurable data output rate
- configurable baud rate (taken from GPS_BAUD variable)
- add support of double and float to ubx parser
- add option to configure RXM_RAW messages (on LEA-T versions)
[dox] add some doc for ubx_ucenter
make-release-tarball.sh executable
[conf] ardrone2_raw: remove wrong NPS_JSBSIM_MODEL

We are still missing a JSBSim model for a quadrotor in X configuration (like the ARDrone2).
The "simple_quad" model is for + configuration.

Now you will get an error starting the NPS sim
(JSBSim failed to open the configuration file: foo/paparazzi/conf/simulator/jsbsim/aircraft/ardrone2_raw.xml).
But IMHO that is better than NPS just not working for no obvious reason.
[docs] update url for styleguide in CONTRIBUTING.md