Dynamic Minecraft version / host port

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.

kolbytn / mindcraft