Return also the product image, to be used by the bundles

[sakiss]

The bundles already have the js functions to update the product image and price.
They just need the data feed to do so. Hence these should be returned in the stockable's json as well.

https://github.com/breakdesigns/productbundles/commit/9ac35ff596a60aea90e37e632ca93ceb7964f97d