camcontrol: Add a sense subcommand

camcontrol: Add a sense subcommand

As the name suggests, this sends a SCSI REQUEST SENSE to a device,
and prints out decoded sense information.  It can also print out a
hexdump of the sense data.

sbin/camcontrol/camcontrol.c:
	Add the new sense subcommand.

sbin/camcontrol/camcontrol.8:
	Document camcontrol sense.

Sponsored by:	Spectra Logic
Reviewed by:	mav
MFC after:	3 days
Differential Revision:  https://reviews.freebsd.org/D43225