* Update Docker docs for 6.0.0-rc2
* Update the docs to match the new Docker "image flavours" of "basic",
"platinum", and "oss".
* Clarifications for Openshift and bind-mounts
* Bump docker-compose 2.x format to 2.2
* Combine Docker Toolbox instructions for setting vm.max_map_count for
both macOS + Windows
* devicemapper is not the default storage driver any more on RHEL