[builder] Add entries for v_omega_diff_drive

Fix issue #184
[mw/socket] Use '' to represent correctly INADDR_ANY

Fix issue #109
[mw/socket] Write a specialized json encoder

This specialized json encoder can encode mathutils structure and
Transformation3d. It allows to store and use more high level structures
in local_data, in particular to represent position (see issue #193).

As a side effect, it allows back to export properly IMU through socket.
[sensor/battery] Don't use time.clock() but time.time() to measure time

time.clock() measures the cpu time of the process, and not the real
elapsed time (which is measure by time.time()).

XXX: not completly correct as it must use the simulated time, but better
than the current code. At least, it fixes the unit test.
[example] Fix the cat_script example after some serialization change

Reported by Jeremy Nicola

While here, update the associated documentation and fix an typo in it.
[doc] Fix json encoding to send command to socket datastream

Reported by Jeremy Nicola
Minor improvement of malformed requests handling
Fix bug when invoking malformed asynchronous service

Previously, the async callback would be set, even if the service
invokation failed. This would cause various error because of
inexisting requests.

While here:
- print traceback for failing service invokation to logger.debug
- fix a minor formatting bug in socket request manager indirectly
  triggered by the main bug fixed by this commit