spiv: Fix action index in image_action_run().

Action parameters are indexed from one not zero.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
spiv: Fix help for arrow keys.

It's 10px by default and 1px with shift not the other way around.

Reported-by: Milan Vancura <milan@ucw.cz>
Signed-off-by: Cyril Hrubis <metan@ucw.cz>