lump-commit of additions from  track cluster splitting ported from 5X to 71X and SLC6 #2961. Porting of cluster splitting in 71X release. Modified for the new tracking.
Merge pull request #3352 from slava77/for-71X-tkClustSplitting-from-taroni-71X_SLC6

Reco -- Track cluster splitting ported from 5X to 71X and SLC6 (recommit #2961)