Provide a simple runner which runs from a folder of images

[ayushbaid]

We have runners for specific datasets, but there is no simple way right now to just run GTSFM on a folder of images.

We can solve this using the following:

1. Reintroduce depricated FolderLoader or some version of it which just takes in a folder of input images.
2. Infer intrinsics from the exif file and the sensor database. If intrinsics cannot be inferred, approximate it from the image shape.
3. Perform fundamental matrix estimation instead of essential matrix estimation.

Additional benchmarks needed for this task:

1. F-matrix estimation for a few datasets.