Restructured configuration system

Configuration logic from node-debug.js moved to config.js
node-debug receive configuration from rc now
config uses yargs argv preprocessor now
Removed conversion part of config.js
Fixed hight priority of node-debug hardcoded defaults
Fixed default web host for node-debug
  (`127.0.0.1` instead of `localhost`)
Fixed null value of web host
  (default web host is empty string now)
Added script option
Added list of avaible options as default help info
I'd rather not duplicate the sample `rc` file, as it may get out of sync easily. Also the configuration can be stored in multiple locations, the project folder is not the only place.

Just point the users to github README:

```
console.log(
  'Configuration can be also stored in a \'.node-inspectorrc\' file,\n' +
  'see README for more details:\n' +
  '  https://github.com/node-inspector/node-inspector#configuration');
```

(perhaps add a different color to the URL if you like)