Extract Kamal::Commander::Specifics to deal with host and role setup and
ensure that primary hosts and roles always come first. This means that
in a rolling deploy we deploy to the primary ones first.
This will be important when we remove the healthcheck step as we want
to confirm the primary host can be deployed to before completing a
deployment for other roles.
By setting the hosts and roles all together in one place we can sort
the primary ones to the front without creating infinite loops.
* main:
Wording
Remove accessory images using tags rather than labels
Update readme to point to ghcr.io/mrsked/mrsk
Validate that all roles have hosts
Commander needn't accumulate configuration
Pull latest image tag, so we can identity it
Default to deploying the config version
Remove unneeded Dockerfile.dind, update Readme
add D-in-D dockerfile, update Readme
Commander had version/destination solely to incrementally accumulate CLI
options. Simpler to configure in one shot.
Clarifies responsibility and lets us introduce things like
`abbreviated_version` in one spot - Configuration.
