Added tuningInfo.js to /app/javascript

--> Contains object 'tuningInfo' with properties:
     --> 'sourceName'  // e.g.: 'Das Erste'
     --> 'sourceID'    // e.g.: '71'
     --> 'onid'        // relevant for tuning
     --> 'tsid'        // relevant for tuning
     --> 'sid'         // relevant for tuning