Added filtering of known files.
Reorganized KnownFileFilterNode to comply with new Node conventions. simplified constructor.
Removed redundant filtering that was added
Removed changes in FileTypeChildren to match state before branching
Fixed mistake made when changing constructor of Known File Filter Node.
Changed text on options panel to Directory Listing instead of Data Result Viewer.
Merge pull request #350 from jawallace/filterKnown

Filter known