[Feature Request] Force users to select a default output directory rather than creating a 'VesselVio' directory on the desktop

[ElisabethKugler]

Would it be possible to force users to either choose an output folder or to automatically create a new output folder in the parent folder of input images?
In the current version, the output folder selection is not very prominent and therefore might result in overwriting of folders if analysis is applied repeatedly.

[JacobBumgarner]

Thanks for contributing this issue, @ElisabethKugler. I think this is definitely a better default behavior, so I will get this implemented.