Added missing uncertainty in the CMS dijet 7 TeV NNLO K factor
In preparation for the tag of the code, I've been revising the implementation of all the data sets. I've realised that the NNLO QCD K-factor for the CMS dijet measurement at 7 TeV was missing the Monte Carlo uncertainty. The uncertainty has been provided by Joao Pires. This PR incorporates this uncertainty (which I'm about to propagate to the NNLO theories stored on the server).
