Improve options to sort and filter results
Both in product tracker and database:
* Remember last sort setting. Default seems to be "last added" while most sellers will have a preference to sort on "sales" or "turnover".
* Extend sorting options with EAN and Price
* Turns columns into filters, especially the column Categories in the product tracker. If your tracking list is long it's not easy to eg filter all non-categorized items or items with two categories attached.