MCgrid: Projecting cross section calculations on grids

Approximately 6 minutes per 1 million Drell-Yan events from Sherpa. This includes both the event generation and the mcgrid computations. The times can vary quite dramatically. The process used in the test case (which is a relatively fast one) takes about 2 minutes 30 seconds for the initial (phase-space fill) run and about 3 minutes for the second and final run. This is for 1 million events on a 2.9GhZ ivy bridge i7.