specify overlap % as a search criteria

[niallmcc]

Often --check-encloses fails because only two of the bounding box corners overlap with the scene. However, there may still be a good overlap (eg over 90%).

It would be useful to specify a filter criteria based on overlap with the bounding box.

Eg 60% allows only scenes that fill more than 60% of the bounding box

[niallmcc]

We also need to be able to stitch together scenes from the same orbit, in this case we can include scenes with small overlaps as long as the area covered in an orbit is above this percentage.