Add CrewRegistryConfig to RigEntry allowing crew members to be defined
in rigs.json and synced across machines. The new `gt crew sync` command
creates missing crew members from the configuration.
Configuration example:
"rigs": {
"gastown": {
"crew": {
"theme": "mad-max",
"members": ["diesel", "chrome", "nitro"]
}
}
}
Closes: gt-tu4
