Added range finder and derivative sensor and modified ray sensor

-Added range finder
-Added derivative sensor
-Copied complete functionality from IRsensor, except sensor
characteristics, to raysensor. Thus, a ray sensor measures the 'real'
length of a beam
-IRsensor is now a derived class of raysensor, extending it with a
sensor characteristics
-Adjusted raysensorbank to fit modified raysensor
Merge pull request #17 from patrickkesper/master

Rangefinder, Acceleration Sensor via DerivativeSensor, IR and Raysensors restructured