Singletop diff
This PR contains the implementation of the ATLAS single (anti)top differential distributions at 7 and 8 TeV. The theory was benchmarked against Jun Gao results. A Data/theory comparison is available here
There are associate pull requests in buildmaster (# 86 e # 87), apfelcomb (# 43) and applgrid (# 7) cc @voisey @mariaubiali