Add a "init_loop_primitive()" method called each time we start a loop primitive.
Add a setup and teardown method to the primitive.
You can thus setup and clean the environment needed by your primitive before and after the run loop.
Those methods will be called each time the primitive is started/stopped.
Merge branch 'master' into pr/13

Conflicts:
	pypot/primitive/move.py
Merge pull request #14 from poppy-project/pr/13

Pr/13