Fix for #34910, NodeGroup input/output sliders bug. Initially i thought this was a limitation of the "only 1 list per panel supported" type, but this has since been fixed. Lists just need an additional identifier to distinguish lists in the same panel, thanks to Bastien Montagne for the uiList overhaul!

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56037 954f8c5b-7b00-dc11-b283-0030488c597c