Create volumes with proper configuration during "docker:start"

[rhuss]

If a volume is refered to during startup in a bind mount mapping and if this does not exist and a volume configuration exists, then this should be taken to create the volume upfront, not relying on Docker to create it implicitly during startup with default params.

This would avoid the necessity to call volume-create explicitly before start when a custom volume configuration is used.

See #985 for a concrete use case.

The documentation needs also an update to reflect that you cannot only configure real host paths in bind mounts, but also volumes (this is also weak in the Docker documentation itself).