EITopPAG updates, merging with E/Gamma features

Here is the full request for the changes to EITopPAG that were requested. This merges a few topics : 

1. Adding only b-tagging to the EITopPAG but nothing else (https://github.com/cms-sw/cmssw/pull/678)
2. Adding the e/gamma changes to the GsfElectron (https://github.com/cms-sw/cmssw/pull/156)
3. Adding Volker's fixes to make it compatible (https://github.com/cms-sw/cmssw/pull/666)

And finally this has a few additions of its own to bring everything together: 

1. In PFElectronTranslator, the isolation from pileup is actually filled. I also fixed a bug from topic branch 666. The python file was not in sync with the EDProducer for the names of the isolation variables.

2. And of course, I changed EITopPAG top projection to use the updated variables.