[services] Make 'supervision' and 'communication' services object

It makes the code a bit more generic, and allow furtherly to implement
asynchronous service
[blender] Factorise init_supervision_services
[pymorse] Fix a race condition between emission and reception of request
[ci] run morse test w/xvfb

- revert to blender 2.64 w/python3.2.3
  to sync with system's python3 version.
- NOTE: increase color depth to 16,
  the default 8 bits is not enough for OpenGL.

Thanks to Séverin Lemaignan for his help!