ofp-actions: Add instructions bitmaps and fix related bug.

This will allow, later, to centralize all of the knowledge of instruction
encoding inside ofp-actions.

OFPIT11_ALL and OFPIT13_ALL are no longer used, so this commit removes
them.  Their definitions were wrong (they did not shift each bit into
position correctly), so this commit is also a small bug fix.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>