- Remove branch 15.x
- Use tomcat:10.1-jre21 for 17
- Upgrade 16.10.x to jre21
- Extract dependency versions to separate objects to avoid duplication

* Update the PostgreSQL examples with the correct locale
* Update the PostgreSQL version to 17 in the docker-compose files as
  otherwise the recommended locale isn't available.

XDOCKER-225: Allow customizing the JDBC connexion parameters + add "allowPublicKeyRetrieval=true" by default for MySQL
XDOCKER-285: Change default MySQL/MariaDB charset + collation to utf8mb4

[Misc] Upgrade PostgreSQL version to 16 (latest stable) in our documentation + docker compose example

* Added missing postgresql docker tag version update for some configs

  * Put new 12.0 version and remove old 10 version not supported
    anymore.

  * Missing update of docker-compose so that the build don't put back
    12.1-alpine

[Misc] Upgrade to latest 12.x version of PostgreSQL to reduce maintenance but also to match the JDBC driver used in the XWiki docker image.

* Use postgresql:9.5 since there's a problem with 9.6 (possibly an incompatibility with the driver version installed by libpostgresql-jdbc-java)

* Removed leftover

* Added posgtreql variants (not working yet)

* 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

'Creating network "xwikimysqltomcat_bridge" with driver "bridge"'

[Misc] Go back to the previous setup which was better and I've found a way to make DockerHub happy with it.

[Misc] Since we may want to generate different images of xwiki in the future (with different dbs, different servlet containers, etc), move all current data into a xwiki-mysql-tomcat directory.

[Misc] Big overhaul to separate image-time setup from runtime configuration + added some license headers

[Misc] Improved README + give a name to the xwiki-data volume + add LICENSE + improved .gitignore file