[testing] Fix proximity test

Fix partially #229
[testing] Rewrite the sick test

The previous test was completly wrong, checking measure done without
calling create_sick_arc() method and these measure were not verified by
hand.

Now, the test pass with both creator api and classic method to create
sick. Fix the last issue for #229.
Re-organized laser-based components

Until now, the code for all laser scanners was in SICKClass.
Refactored code to:
 - create LaserScannerClass in sensors/laserscanner.py
 - make all laser based sensor rely on this common parent class
 - update the doc to have explicitely a generic laser class and preconfigured
   laser scanners (and also, to make it hopefully a bit easier to read)
[doc] gallery macro: do not try to display images for directories
[builder] wrap bpy calls in bpymorse