Docker image with software update

**Type of Feature**:

- [ ] Collaboration or partnership
- [X] Improvement or clarification
- [ ] New Processing 

**Description of Feature** 

- post a docker image with latest Xponents REST API (and Solr Server)
- document how to deploy using docker-compose, mapping external `xponents-solr` volume in at runtime

objective -- cut docker image down to 500mb or so.