[Fuze+] imageviewer: update/complete keymaps

1) update/complete keymaps (now handle slideshow)
2) update/complete manual

Change-Id: I1baf2598941bb781a2f2777f23eb543bd6bf5848
Reviewed-on: http://gerrit.rockbox.org/354
Reviewed-by: Amaury Pouly <amaury.pouly@gmail.com>
2 files changed