- pasc-video-matching app extracts frames using a thread pool

- added a function to read PaSC (NIST) xml sigsets
Fitting: Moved convertAvailableLandmarksToClipSpace to a dedicated function
detect-landmarks now works on PaSC video frames with the PaSC-video-PittPatt-detections landmarks from the csv file.

Note: The input frames have to have the name "name.framenum.ext"
detect-landmarks: PaSC frames: Now works with both zero-padded framename-filenames (e.g. frame.003.png) as well as non-padded (frame.3.png)
detect-landmarks now outputs an info message when no landmarks are found
detect-landmarks: Added imageio logging
Merge branch 'PaSC' into learn-frame-extract