Additional sort order field for filaments#681

Hi There.

Might not be an often requested thing but is there a way to be able to show the purchased date in the filament listing rather than the created date?

I have only just started using SimplyPrint and a lot of my filaments predate the created date but I find that the filament order by created date rather than purchased date which is not necessarily correct in my circumstance

Sounds reasonable. Will implement this tomorrow! :)