Allow passing two different asset URLs for upgradable goods - one for the upgrade and one for the progress bar
- Assign unique "item_" prefixed IDs to all new models
- Don't reshuffle item IDs of upgrades when renaming an upgrade
- Reorder and reset upgrades every time an upgrade is added, removed or reordered
- Don't reorder upgrades when changing the upgradable's item ID
Fix initial progress bar asset bug
Merge branch 'upgrades' into dev
Fix deletion of categories, currencies, goods & packs - do it by triggering a destroy event to leverage Backbone Relational