whole_func_string: function (plugin, manifest) {
      if (config.plugins === undefined) {
        config.plugins = {};
      }
  
      config.plugins[plugin] = {
        name: manifest.name,
        displayName: manifest.displayName,
        version: manifest.version,
        description: manifest.description
      };
      configHelpers.saveConfig();
    }
func_code_string: function (plugin, manifest) {
      if (config.plugins === undefined) {
        config.plugins = {};
      }
  
      config.plugins[plugin] = {
        name: manifest.name,
        displayName: manifest.displayName,
        version: manifest.version,
        description: manifest.description
      };
      configHelpers.saveConfig();
    }
func_documentation_string: Add a new plugin to the configuration file.
  The configuration file is written in JSON.
  It adds an entry to the plugins field.
  Name, display name, version and description are required.
  
  @param {String} plugin The plugin name as it's typed by the user.
  It s in the form user/repo.
  @param {Object} manifest Manifest containing plugin fields.