Add confirmation prompt to deletion action

[RayJW]

This is my WIP attempt to resolve #1136, but it isn't working at the moment. Clearly, I don't understand Rust and the whole borrowing logic enough for me to resolve this at the moment. I tried many different things but can't get the logic "Rusty" enough. At the moment, the issue is that the &appwindow reference in trash.rs doesn't live long enough. I tried creating a clone, among other things, but that didn't help either.

Other than that, I tried to copy the style of the other dialogues as much as possible to keep the whole architectural idea the same.

I'll keep working on this sometime, but in the meantime, if someone knows how to properly do this, feel free to point me in the right direction or open a PR.