Improve region-of-interest workflow

[mohamedtahaguelzim]

Current ROI workflow is painful, as demonstrated by the forum reviews.
To setup ROI, I suggest the following steps:

1. Once all is calibrated, load the stitched panorama, and pan automatically to the left (exact pan angle would be either automatic or approximate).
2. Have the user click the left two corners only
3. Automatically pan to the right corners
4. Have the user click the right two corners
5. Since the panorama is supposed to be straight, the corners should be enough
6. To find the required "points" for the left and right frames (as each FrameSource must have it's own polygon ROI), we'd infer from the (default/automatic) seam. Since we do not really benefit from having each polygon be on the exact left/right halves of the field, this should be fine.
7. An unprojection step will be required. Thus this issue builds on top of the work of @uSpike at PR GUI ROI #329.

This can also extend easily to non GUI apps, through a browser interface, using ThreeJS or any tool that allows for easy reprojection. This is proven to be doable, thanks to the v1 archive of this repository https://github.com/reco-project/video-stitcher-v1