HI updates for mixing in RelVal

The following updates are implemented:

-The vertex matching is fixed, and it's put into uniform format between standard vtx smearing modules, PbPb mixing and pPb mixing.
-The matrix is updated to have the correct options.
-Mixing-related modifications to standard sequences cleaned up.

Although independent, the pull request is needed before PR #1564 so that the needed RelVal operations can function properly. We need a RelVal production with this PR, and then another RelVal after PR #1564 is also merged. Details in:
https://twiki.cern.ch/twiki/pub/CMS/HiValidation53Xcontacts/03.02.14_DailyHIValidation.pdf