Use git for ibt-build scripts.
Merge pull request #514 from ktf/use-git-int-build

Use git for ibt-build scripts.
Add das cache file.
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