Updates #169. Adding full population of the FilterLibrary tree with all
the filters. Drag-and-Drop of filters from the tree to the Pipeline
works. Fixed bug in the FilterList that was causing the FilterList to
scroll to the last item when any item in the list was selected. We have
now decoupled the FilterList from the FilterLibrary widget. They are
both views into the same data model so we are going to treat them as
such. Added ability to the FilterList widget to search by plugin, group
and subgroup name and those are on by default.