fix drich segmentation

Debug dRICh cellID, and any other readout issues

Changes:

• fix buffer overflow in segmentation specification
• adjust segmentation definition:
  • make x,y indicators unsigned
  • ensure a 16x16 matrix of pixels is defined on each sensor
  • fix x,y indicator mapping (sensor orientation issue)
• changes validated with pixel hit distributions, from decoding cellID directly

Example pixel distribution (1 box = 1 sensor module, 1 histogram bin = 1 pixel, each sensor has 16x16 pixels):

Any apparent module misalignment is not real; it's an artifact of projecting spherical sensor placement to a plane