GENIE:GENIE Tuning rel-2-6

=Tunings of release 2.6.n=

The code was branched at release 2.6.0 with the intention of tuning the model. A number of improvements were performed on the trunk before the tuning strategy was finally agreed and it was deemed more appropriate to tag a new release at 2.7.0 for the tuning branch point. Please see GENIE_Tuning_rel-2-7 for details of the tuning of the model at this point.