Issue: 🙏 Feature request | FEWarp Constraint assignment support

[stevenlabelle]

Request 1: Include units or clarification whether the range_min, range_max, and size parameters in the property tab are in pixels or physical dimensions. Similarly add a clarification to the blur parameter (is kernel width in px?).
Request 2: Support assignment of imported images to template and target images.
Request 3: Automatically pull size values from image data.
Request 4: Support of .tif files.