Add an option to compute the hases on some user input in the hashes tab in explorer

[0ibaba]

The problem I'm facing is that if I'm checking the hash of a somewhat relatively big file and I have multiple hashes selected, explorer hangs. So it'd be nice to have an option to compute the hashes so that I can select the hashes and then check them. I know this might not be a super useful feature, but it'd be more convenient. This problem is also there with the context menu entry as both checks the previously selected hashes.

Right now I have to check the hash of a smaller file, select what hashes to compute and then check it with the bigger file.

[namazso]

The real problem here is the hanging. In theory that shouldn't happen and then canceling would work.