change the naming convention of CaloMETs

Continuing from https://github.com/cms-sw/cmssw/pull/4114, this PR removes "corMetGlobalMuons" from the RECO sequence and the event contents of RECO and AOD.  The new name is "caloMetM", which was already added to RECO and AOD at https://github.com/cms-sw/cmssw/pull/4114 and included in [CMSSW_7_2_0_pre1](https://github.com/cms-sw/cmssw/releases/tag/CMSSW_7_2_0_pre1). This PR also replaces "corMetGlobalMuons" with "caloMetM" in various files.