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
How about this:
```js
Config.filterOptions = function(filterExpression, options) {
  var filteredOptions = {};
  
  Object.keys(options)
    .filter(function(key) {
      var value = options[key];
      return filterExpression(key, value);
    })
    .forEach(function(key) {
      filteredOptions[key] = options[key];
    });
  
  return filteredOptions;
};

Config.filterNodeDebugOptions = Config.filterOptions.bind(Config, function(key, value) {
  var dashedKey = keyToDashedKey(key);
  var definition = definitions[dashedKey];

  if (!definition || definition && definition._isNodeInspectorOption) return true;
});

Config.filterDefaultValues = Config.filterOptions.bind(Config, function(key, value) {
  var dashedKey = keyToDashedKey(key);
  var definition = definitions[dashedKey];

  if (!definition || definition && definition.default !== value) return true;
});
```