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
For me, the first way (where default value is not  changed  to `''` is preferable, because we don't have unexpected value in `web-host`, in any time it is a true ip - `0.0.0.0` or `127.0.0.1` or configured like this `node-debug --web-host 192.168.0.100`). So, is it needed to handle `''` value in this case?