[pymorse] Added a check for invalid component names

If a component name does not contain the full hierarchy of the robot,
it's  a bug in the MORSE cmpt renaming code
Removed builder.creator.RobotCreator

This class simply created an empty robot, but was broken because
the resulting component did not inherit of builder.Robot.

Better to remove it completely.
Now, when creating a robot *without a Blender model*, an Empty is added.
This makes the FakeRobot (the only user of RobotCreator) a real robot, and
should fix bugs (because, as a RobotCreator instance, it was not considered
for automatic renaming, and thus its sensors/actuators would not be
accessible from pymorse for instance).
Turned MakeHuman into real Robot-like

This is made possible by commit c25b05e
[makehuman] Fix positioning of IK targets