Implemented sumpT dismabiguation for VBF and untagged categories.

Fixed #351
Also cleaned up duplicated code for diphoton pair selection.
Merge pull request #352 from musella/topic_sumpt_vbfuntag

Implemented sumpT dismabiguation for VBF and untagged categories.
Merge branch 'master' of github.com:h2gglobe/h2gglobe into synch_20131215
small fix