New interface for KrCalib

DataFrame based functions for map manipulations (eliminates old class KrEvent which was inefficient).
Maps for SiPMs.
Possibility to define Energy and Z as "variables in the Data Frame"), so that one can use energy in PMTs or charge in SiPMs (or use Z induced from RMS).

First working version

Merge pull request #24 from ausonandres/add_time_parameters

Add time parameters