Simulator/Physics: Add test cases for DistanceSensor

[josefbehr]

DistanceSensor seems to be not working correctly (small errors between visualisation and measured values?), should be tested automatically, since the sensor will probably be used in experiments!

[josefbehr]

Why does the DistanceSensor not provide its own box for representation in simulation and collision calculation? Should this be added to remove scripting overhead (as is done in the LightSensor)?
@cybott any comments regarding this?

[josefbehr]

TODO:

• remove DeadZone and Range parameters, replace with RayLength and automatic exclusion of parent objects from collision calculations
• code refactoring
• automatically add a box geometry representing the sensor object
• finish test cases for DistanceRay, write some for the sensor itself

[josefbehr]

Although the refactoring went great and the code as well as the scripting setup for the sensor are much cleaner now, I can for the hell of it not figure out, why, in the changed version(s), the collision rule returns no collision points.

@cybott maybe you have a little time to throw a look? to me all seems perfectly ok, but no collisions are reported.

Current working version: https://github.com/nerd-toolkit/nerd/blob/master/nerd/simulator/simulator/Physics/DistanceSensor.cpp
Refactored version using new SensorBox base class: https://gist.github.com/josefbehr/4755105aca2c86fbfdf1
A version without using DistanceRay, but collision objects and geometries directly shows the same problem.

If no solution is found in the next few days, I'll revert to the current git version and just try to clean it up a bit (in addition to tests).