Add mosaic meta to /mosaics and /models endpoints

[vgeorge]

The endpoint /mosaics is returning ids only, requiring additional requests to /mosaics/:id endpoint to fetch metadata. It would be nice to change /mosaics endpoint to include all metadata from mosaics to avoid this flow in the front end. This is a breaking API change.

Another enhancement required by multiple imagery selection in the front end is to include a property imagery_id to the model.meta object of /models endpoint, which will allow matching base imagery of a model.

cc @geohacker @ingalls