* Fix README to follow guidelines from Dockerhub + small improvements

* Added logic for configuring an external Solr instance using environment variables
* Updated README.md with instructions for using the XWiki image with an external Solr instance
* Added a script, contrib/solr/solr-init.sh, which initializes a Solr container to be usable by XWiki

* Improved docker-entrypoint.sh by adding compatibility for docker secrets
* Updated README.md with examples of using the XWiki image in Docker Swarm along with Docker secrets and Docker configs

Pointing to the latest release.

* Update documentation accordingly

* Update documentation and provide an example compose file for postgres

* More progress, still not working. I have an issue with "jdbc:postgresql://replacecontainer:5432/replacedatabase" not working and generating " Caused by: java.net.UnknownHostException: xwiki-postgres-db"
* Added ascii art in Dockerfile
* Renamed containers so that we can run several xwiki images on the same machine without conflict

* Use a better name for the property (thanks to Tianon)

* Prepare the field by generifying the templates/build and docker files

 * FIxed missing modification from past commit

[Misc] Improve doc (was committed as part of "XDOCKER-13: Add an image tag for XWiki 9.0 and publish on dockerhub" on the 9.x branch)