Bch cleaning

I added flags for performing the BCH cleaning of jets. 

I saved separately the BCH_CORR_CELL variable which can be used to study the impact of the BCH issues, as well as the flags for each possible cleaning cut, including the systematics. The flags include:
* isBadMediumBCH
* isBadMediumBCH_up
* isBadMediumBCH_dn
* isBadTightBCH