Slow hash on large destination paths

[keybraker]

On the current solution, system goes through the entire destination path and hashes all the files in it. This means that for destination paths with a lot of files, it takes a lot of time and memory to hash all the images.
This is not only slow but not a good solution as well, as if only one image is to be moved the whole destination path is hashed for one image.

This should change and the hashing of a path should only happen when a destination path is decided for an image. This can also be cached in order to not have double hashing of same destination paths.