Protections for jets and MET for PFEGamma and customize function to switch on PFEG in ParticleFlow

built ontop of: CMSSW_7_0_X_2013-10-25-0200 + ged_egamma_isolation (https://github.com/cms-sw/cmssw/pull/1174)

Includes protections for jets and MET when using PFEGamma.
PFEGamma is still turned off by default.

@slava77 how do you want me to provide the changes to activate PFEGamma inside of particle flow?

All matrix tests passed in standard settings.

All matrix tests passed using the following customization to switch on PFEG:
```
runTheMatrix.py -s --command="--customise RecoEgamma/Configuration/customizePFforEGammaGED.customizePFforEGammaGED" --useInput=all
```