[cmake] Include ctest instead of just enable_test

It allows a lot more versatile targets for testing
[doc] Fix a few old statements in basic tutorial
[doc] Fix another 'now-incorrect' statement in basic tutorial
[builder] Fix get_child() to work recursively

This fix broken BarePr2.set_color()
Let users set the Morsy body color

This can be useful we running tutorials with many Morsy instances, one
per user
[doc] Document which files are not licensied under BSD-3 clause

Moreover, add a copy of Open Font License
Clean up messages with !!!!!!

While here:
	- try to wrap long lines
	- remove unused import
	- remove useless whitespace

Fix #242
[sensors] Fix typos in data field description of velocity
[actuator] Add an abstract method to deal with velocity or position control

Part of #117
[actuator] Add a property ControlType to various actuator

This property is used to decide if the computed speed controls the robot
in Velocity or in Position. The default is still Position, but it is now
easier to test each robot with different settings.

Part of #117
[testing] Add a basic test for velocity sensor

A bit touchy due to the 'Velocity' control, but I do my best to make it
reliable

Fix #336
[core] Remove some now unused code in datastream

The code was needed to load extra methods and to clean them up. Now,
with the object model, it is not needed anymore.
[doc] Remove deprecated import
[testing] Add a target in rotorcraft_waypoint

Regression test for #370
[core] Improve wrapper against mathutils.Matrix

In particular, it now includes the static method Rotation.

Fix #370
[core] Rework the previous commit which breaks camera sensor

Repeat after me, you will pass all the tests, all the tests ...
Indeed, the new solution is cleaner, shorter, and complete by definition
!
[service] Add new service to control the logging devel of a component

Part of #337