Enh undistort videos
- New option under image_data_handling: Undistort videos. Enables user to automatically remove lens distortion of 1 or many folders.
- User can choose codec (currently only h264 and unencoded) when doing undistort/convert video
- Added info above to website
- Added several points to FAQ on website
- Updated README.MD and website to include opencv2 and ffmpeg on PC installation. TODO: Update autoinstall files for Windows and Linux
- Let user know of problem when trying to do multianimal tracking with px/mm = 0