[Enhancement] user feedback when relocating files fails

[maxwell1755]

Is your feature request related to a problem? Please describe.
If you try to move an image from one file to another, and there is already a copy of the file there, the program appears to fail to attempt anything. This can be an issue when relocating files, especially if you misclick and copy to the destination instead of move

Describe the solution you'd like
A popup, prompt, or message of some kind saying that the files already exist in that location so the transfer was aborted. Or, if possible, a prompt to replace the existing files in the destination.

Describe alternatives you've considered
after discovering that this was the issue, I can manually delete the copies by seeing what I have 2 of.

Additional context
While trying to organize my images, I must have accidentally copied a set of them to the destination instead of moving them. I didn't realize this at first though, so to me it appeared as if they simply failed to move. When I tried to move them, again I found that they still refused to move, this was because there was already a copy in the destination although I didn't know it yet. This especially confused me because some files would move just fine, and I was about to make a bug report on it thinking it had to do with the recent changes in 6.1.

[RupertAvery]

Should be fixed by #229

This makes it so that if there are existing files in the destination the new files will have a number appended