Make console-only mode a proper subset of headless mode

Let's not make the mode space too complex. Do we really want to have to ponder
what it means to be console-only but not headless?

Make it so that turning on console-only mode also turns on headless mode (with
dialogsAreFatal turned on, too).

Change-Id: I630cb1bc605c1fb1787ace58180125509ef8789b

vcl/source/app/svapp.cxx

@@ -1512,6 +1512,7 @@ bool Application::IsConsoleOnly()
 
 void Application::EnableConsoleOnly()
 {
+    EnableHeadlessMode(true);
     bConsoleOnly = true;
 }