New metadata format
requested to merge more_efficient_metadata_for_new_commondata into final_reader_for_new_commondata_mk2
Created by: t7phy
This PR implements CMS_ttBar_8TeV dataset with the new metadata as discussed in Ams code meeting. @scarlehoff this builds upon the commondata reader branch, however, could you please tweak the reader script in this branch and test out if it works on the new format? backward_compatbility.yaml in the buildmaster directory is the dictionary as you had proposed, please have a look at that too.