Easier to find downloadable files

[ripperdoc]

One or several of:

• Ability to sort orders from last changed (but just adding files to a product won't update the Order)
• Some search filter that can be linked to focus on specific orders, e.g. my_orders/?title__startswith=kopparhavet
• In My Products/library, better highlight downloadable files and also allow by sort on changed (and/or show "New" badges)

(both products and orders should have fully capable sorting/filtering tools)