KAZOO-3214 Crossbar access to third_party_bigcouch call recordings

While there is a feature for storing call recordings in third party BigCouch, there probably could be useful to have an access to these recordings through crossbar. 

Looking a bit ahead, it looks like it could be good to create a crossbar module which provides access to different type of data located at third party BigCouch. 

Please accept initial pull request if you feel that it could be of any interest