refactor delete/confirm to separate class

[marc-vdm]

Issue

We have multiple instances of delete/confirmation dialogs right now for deleting things (#1138 and #1190).

We can probably refactor this to 1 class that takes some strings and the if_confirmed function as inputs to customize. This can clean up the code a bit. We may also want to apply this the project deletion, which currently has it's own dialogs.

When doing this we should probably make the final confirmation optional.