Add Filament bundles

[Fynniboyy]

I regulary buy filament spools in bundles because it's a bit cheaper. It would be amazing if I could add such a bundle to spoolman so that I don't need to add each spool one at a time. This is especially annoying if there are different colors in a bundle.

Key Aspects:
Adding multiple spools that are different at once
automatically calculate the price for each spool from the bundle price
treat the spools as regular spools, once they're added