Storage backend to use a MataNui server for data and meta-data

The MataNui server is a RESTful web service fronting a MongoDB/GridFS server. It can be used to store/retrieve/query data and meta-data, so it could replace a WebDAV (meta-data) server as well as data stores. The advantage of the MataNui server is, that it can be a local (to the LAN) front end to a federation of MongoDB instances, which can be geographically distributed. This ensures fast access and low latencies as the data is automatically replicated between the sites, and users only access their closest/fastest MataNui service.