LMVM: Add histograms and restructure comb. BG procedure
- add new PLUTO path (Tetyanas folder)
- add purity histograms
- add histograms to investigate diff. between PLUTO/UrQMD and electron/positron
- add comb. BG histograms in LmvmDraw.cxx
- add histogram to investigate BG and its different sources
- add histograms for acc and rec. pions and electrons for var. detector combinations
- some more small changes