First series of cleanups (for MSSM) on the postfit plos

- Note I've set the maximum x-axis range to 1.5Tev as default now, as long as we are investigating the tails in MSSM.
- chi2 has been returend to the milder version that takes the residual fit uncertainties into  account.
- htt_mm now has a special option on produce_macros.py to add stat uncertainties on all templates and to remove all shape altering shifts (to be used when creating postfit plots from msv inputs).