code: public Plugin getPlugin(String artifactId) {
          Data dt = getData();
          if(dt==null)    return null;
          return dt.plugins.get(artifactId);
      }
docs: Gets the information about a specific plugin.
  
  @param artifactId
  The short name of the plugin. Corresponds to {@link PluginWrapper#getShortName()}.
  
  @return
  null if no such information is found.