Request feature for subset images scene generation from full sfm scene data

[WindyYam]

Currently if I remove some of the images from the full set of colmap scene it will report error and refuse to go on.
It would be helpful if we can manually delete some of the camera images and still be able to build the scene, just print some message to remind the user some images missing. Such that we can divide a very large scene into small scene chunks, e.g. several individual rooms of a whole house colmap data, and so we can limit the total gaussians in each of the scene chunk