Added transparent white overlay that is drawn over window when it does not have focus
Focus is now required for on_mouse_over-events even if the windows is the topmost
Separated horizontal and vertical alingments so that vertical alignment has correct names (left/right -> top/bottom)
Handlers can now access components and change their states
Fixed an issue where label text would not respect the original size of the label and would increase it if text texture size was too large
Changed test to use the new handler registration style