Migrate Docker Libary documentation to KB

This got too big for https://hub.docker.com/_/mariadb/ "Note: the description for this image is longer than the Hub length limit of 25000, so has been trimmed"

Source contents: https://github.com/docker-library/docs/tree/master/mariadb

Too big for single KB page so suggested breakdown:

Rough thoughts on pages:

• Starting the MariaDB container
• Initializing the MariaDB container
• Customizing the MariaDB configuration
• Environmental Variables reference
• Common tasks:
• Backup and Restore
• Configuring Replication
• Healthcheck script for liveliness and readiness

greenman can you provide some guidance on creating a new set of pages (or just create them). I'm happy to fill/edit these however any assistance most welcome.