met uncertainty tool (in PAT) fixes for 72X releases

The MET uncertainty tool in PAT has been updated accordingly to the last development changes in 72X releases, and can go to the central release now.

Pat MET names have been also updated in order to match the new naming convention.

Matthieu

@TaiSakuma : used in https://github.com/cms-met/cmssw/blob/53X-MVaNoPuMET-20140606-01/RecoMET/METPUSubtraction/src/PFMETAlgorithmMVA.cc for example

It is redundant, but much easier to use in an algorithm code rather than arctan(y/x) and it does not use so much memory. we don't want to remove phi for other 4-vector as we already have x/y components, so I think it is easier for developers of MET algos to keep the phi variable in CommonMETData