Migrating the EITopPAG changes to 700pre2

This is to fix the mangled tag here : 

https://github.com/cms-sw/cmssw/pull/346#issuecomment-22686647

Please take this one for pull request. 

The changes include : 

- Changes to the EITopPAG sequence to account for latest top PAG request : 
  - Use delta-beta corrections in top projection for electrons
  - Add b-tagging. 
  - This necessitates a dataformat change to GsfElectron to add the PU isolation that is computed in RECO