Add a DRYRUN=1 and a INTERACTIVE=1 option to running zwift.

[netbrain]

DRYRUN This will simply print the docker command that it would execute if DRYRUN was not specified. Makes it easier for people to debug containers.

INTERACTIVE This will replace the -d flag with -it and set --entrypoint bash so that the container becomes fully interactive and it's possible to debug step by step within the container. This would also make it easier to debug issues within the container.