QC8 reco and analysis improvements

Several fixes and improvements for QC8:

• multiply by 10 all geometry sizes (were of incorrect units);
• add front chamber geometry (previously we had back only) and rename the qc8 geometry to qc8-back;
• add and residual fit;
• add code for alignment (not yet working);
• plot HV scan results;
• plot digi occupancy.

Additionally, this fixes an error in the chi squared calculation (valid for all setups).