Yaocho APIs

This adds a few APIs that were useful for Yaocho. These need to get to prod before I can put Yaocho in the marketplace.

r?
I was hoping something like `http GET 'kitsune/api/products/?visible='` would make visible `None`, but I was wrong. I was hoping to achieve a trinary filter. Since I didn't end up using this, I'll nix it and worry about it later.