added incremental id to cart model, removing still not working
fix removal of cart items
VE-646 Switch approaches from using incremented ID to using temporary filename as identifier, move logic into model method
remove extraneous code
VE-646 code review adjustments, mostly cleanup and removing extraneous code
VE-646 move assignment into conditional branch
Merge pull request #2248 from Wikia/VE-646-new-approach

VE-646: Renaming a media item in the VE's Add Media dialog breaks the cart and the cart item