Add filter to item before template

It isn't currently possible (as far as I'm aware) to filter an item before it gets sent to the template (using Ajax).

It can be filtered using "edd_cart_item" but only *after* the template has been set, an item cannot be modified before this. Would be useful is custom options have been set in the item.
Merge pull request #931 from elliott-stocks/patch-3

Add filter to item before template