KTAG sector multiplicity

This algorithm aims at rejecting the non-kaon component and it corresponds to a cut on the number of KTAG sectors fired in time with respect to the L0 trigger.

The cut tested on 2014 data (run 1520) is: NSectors > 3 (see pag 22 here). A new version of the algorithm with NSectors > 4 has been deployed on NA62 PC-farm during 2015 run.