initial work on frame navigation SL#4660
Frame navigation through keyboard

Left-right keys should be used for clockwise navigation arround the
frame. The Enter/Return key is used for buttons which have clicked events.

Signed-off-by: Guillermo Trinidad <gui.trini@gmail.com>
Reviewed-by: Daniel Francis <francis@sugarlabs.org>
Merge https://github.com/trinidadg/sugar