Simplify and extend automatic screenshotting

Now includes 2 'outlier' analysis effects, and has simpler code.
The tricky capture cases are now first in the list.
Vocorder and Chirp are now included.  Comma was missing between them.
Now gives error report for an unknown command.

src/commands/ScreenshotCommand.h

@@ -56,6 +56,9 @@ private:
 
 public:
    static ScreenshotCommand * mpShooter;
+   static void (*mIdleHandler)(wxIdleEvent& event);
+   static void SetIdleHandler( void (*pHandler)(wxIdleEvent& event) ){mIdleHandler=pHandler;};
+   static bool MayCapture( wxDialog * pDlg );
 
    void CaptureWindowOnIdle( wxWindow * pWin );
    wxTopLevelWindow *GetFrontWindow(AudacityProject *project);