Protections against high pT pions becoming tracker-driven only gedGsfElectrons

Built ontop of CMSSW_7_1_X_2014-01-30-0200.
Developed in 700_pre12 + tracking changes and egamma changes for pre13.

@dbenedet please add plots

This pull request contains an update to gedGsfElectron producer to harmonize the pre-selection of tracker-driven-only gedGsfElectrons above 50 GeV.

In private tests we saw an improvement in the fake rate for tracker-driven-only GSF electrons and no change in efficiency for electrons from Z>ee. 

We would like to request a backport into CMSSW_7_0_X as soon as possible.

@nclopezo This will need manual testing since it requires you to download a new weights file.
@slava77 We should queue this for CMSDIST.