code editor: save as and set command prior to execution of new file (if file extension can be mapped), fix #1908

 Includes inline-watch upon filecount/filelist if a watch_id is given.
 The watch handels are identified by window_id, view_id (both set automatically) and watch_id of choice.
 Upon changes a "watch" message will be send via bus containing further details (action, watched path, watch_id).
 Also prevent multiple filelist updates from running simultaneously and improve overall update triggering.