MATLAB update and encoder setPosition() added.

-MATLAB updated to be able to set the encoder position, and the wall
position.
-added "current" and "target" to the PID structure, to make the debugging
easier.
-fixed the reduction ratio (15 -> 16.5).
-it is now possible to set the encoder positionm using an offset settable
from MATLAB.
-made the default coefficients of the position PID less agressive and safer.