Dynamic Minecraft version / host port

[Nimikita]

Added functionality such that if in settings.js:

• If "port" is -1, the Minecraft LAN ports are scanned on the host for a LAN server.
• If "minecraft_version" is set to "auto", it'll use the server version for mcdata and joining.

Changes:

• Added mcserver.js, responsible for new server-related functionality. (Retrieving a valid server, pinging, and error handling.)
• mcdata.js now exports a class with mc-related functionality.
• Host, port, and version are now passed to agent processes and now used instead of settings.js during bot init.
• Added better error handling for server/version issues:
  • Server not found.
  • Server is using an unsupported Minecraft version. (Then lists compatible versions from minecraft-protocol.)
  • Server doesn't use expected Minecraft version.