Add CMSSW_7_3_DEVEL_X IB.
Remove CMSSW_7_2_DEVEL_X.
Merge remote branch 'origin/IB/CMSSW_7_0_X/stable' into IB/CMSSW_7_0_X/stable
Merge remote branch 'origin/IB/CMSSW_7_1_X/stable' into IB/CMSSW_7_0_X/stable