added optional close button to sub-panels...

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>
made close button auto hide + some unification of panel mechanics...

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>
some cleanup...

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>