Remove openloops from sherpa.
Merge pull request #1250 from nclopezo/remove-openloops-from-sherpa

Remove openloops from sherpa.
Merge remote branch 'origin/IB/CMSSW_7_3_X/stable' into IB/CMSSW_7_0_X/stable
Merge remote branch 'origin/IB/CMSSW_7_3_X/gcc491' into IB/CMSSW_7_0_X/stable