Cleaning of pat::MET data format

[mmarionncern]

Remove unused old format functions from the header file.

Do not affect any sequence nor physics.

[cmsbuild]

A new Pull Request was created by @mmarionncern for CMSSW_7_4_X.

Cleaning of pat::MET data format

It involves the following packages:

DataFormats/PatCandidates

@cmsbuild, @vadler, @monttj can you please review it and eventually sign? Thanks.
@gpetruc this is something you requested to watch as well.
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@Degano you are the release manager for this.
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[gpetruc]

Was there any reason to rename uncorrectedPt to uncorPt (and the same for the other methods), thus breaking compatibility with existing analysis code calling them and existing documentation?