nc-multiplex: Startup should overwrite netcreate-config.js and auto-compile

[benloh]

The nc-multiplex startup should:

1. Automatically compile netcreate
2. Set up the correct netcreate-config.js

This is necessary because:

• If netcreate-2018 is compiled using npm run dev autoreload will be on and cause websocket errors.
• If netcreate-2018 has not been compiled, or was previously compiled using a previous version, any databases opened will be using the wrong version of the code.
• If the last netcreate-2018 run (e.g. via npm run dev or nc.js) was done with a specific dataset, ip address, port, or websocket port, those settings will be used as the base dataset.

See also #105.