Added bookmarks support to PathVectorParameter uis.
Added bookmarks support to PathVectorParameter uis.

This is duplicating code from PathParameterValueWidget - depending on what people think of refactoring the previous commit, we could probably get this to be shared somehow.

andrewkaufman/gaffer,johnhaddon/gaffer,ivanimanishi/gaffer,goddardl/gaffer,davidsminor/gaffer,cedriclaunay/gaffer,cedriclaunay/gaffer,hradec/gaffer,johnhaddon/gaffer,davidsminor/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,boberfly/gaffer,boberfly/gaffer,appleseedhq/gaffer,appleseedhq/gaffer,lucienfostier/gaffer,hradec/gaffer,ImageEngine/gaffer,ivanimanishi/gaffer,hradec/gaffer,ivanimanishi/gaffer,GafferHQ/gaffer,chippey/gaffer,GafferHQ/gaffer,ImageEngine/gaffer,lucienfostier/gaffer,goddardl/gaffer,GafferHQ/gaffer,GafferHQ/gaffer,boberfly/gaffer,lucienfostier/gaffer,cedriclaunay/gaffer,ivanimanishi/gaffer,andrewkaufman/gaffer,appleseedhq/gaffer,boberfly/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,lucienfostier/gaffer,chippey/gaffer,hradec/gaffer,appleseedhq/gaffer,goddardl/gaffer,ImageEngine/gaffer,chippey/gaffer,davidsminor/gaffer,andrewkaufman/gaffer,cedriclaunay/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,davidsminor/gaffer,hradec/gaffer,chippey/gaffer,goddardl/gaffer