Save persistent data in server backups

[danhale-git]

It would be useful to remember the port a specific server was launched on. Persistent server information is useful in general and could probably be included in the server directory without causing any problems.

Create a struct representing the craft server.
Use it from the craft package.
Marshal/unmarshal to json and store in the bedrock directory.
Add the json file to the serverFiles array for consumption when backing up.