Valama: Moving GDL stuff to widget
Fix gdl appearance (fixes by Linus) and handle --layout as ro.

 * Gdl appearance fixes:
   - Show all widgets before laoding layout. Otherwise only closed items would
     be visible.
   - Show main window before adding widgets to open it full screen to not
     screw up gdl layout.
 * Make --layout file read only again.
 * Show some better debug and error messages (gdl layout loading).