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

This is a cherry-picked version of: https://github.com/cms-sw/cmssw/pull/1177

built ontop of: CMSSW_7_0_X_2013-10-31-0200 ## note this is in the future! no testing until 10-31-0200 is available

Includes protections for jets and MET when using PFEGamma.
PFEGamma is still turned off by default.

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
```