Added support for executing selected node in History View
Added support for executing selected node in History View

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gui/version_view.py
 class QVersionTreeView:
   In set_action_links()
     added execute rule
   New methods:
     can_execute()
     execute()

hjanime/VisTrails,minesense/VisTrails,VisTrails/VisTrails,celiafish/VisTrails,VisTrails/VisTrails,minesense/VisTrails,Nikea/VisTrails,celiafish/VisTrails,minesense/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,minesense/VisTrails,hjanime/VisTrails,minesense/VisTrails,hjanime/VisTrails,hjanime/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,celiafish/VisTrails,VisTrails/VisTrails,Nikea/VisTrails,Nikea/VisTrails,celiafish/VisTrails