Explicit L1 match in single tkmu trigger

Modifying filter for single tracker muon trigger to accept L1 collection as previousCandTag and do geometrical matching between HLT and L1 muons.  This is to avoid ambiguity as to whether the muon passing the HLT really did pass the correct L1 trigger as well, a necessary assumption to factorize the L1 and HLT efficiencies.  This was discussed with Hugues Brun, muon HLT contact.

Practically this has very little impact.  I tested on a few thousand Wmunu MC events and saw no difference compared to the previous behavior.  

The code is backwards compatible - if no L1 collection is given, no L1 matching is attempted.