Doc: described storage-driver options in cli reference
Doc: described storage-driver options in cli reference

Documented --storage-opt=[] option in cli reference page. Content taken
from:

  daemon/graphdriver/devmapper/README.md

Signed-off-by: Michal Minar <miminar@redhat.com>

Docker-DCO-1.1-Signed-off-by: Michal Minar <miminar@redhat.com> (github: SvenDowideit)

ashfall/cli,dnephin/cli,docker/cli,Zebrilee/cli,thaJeztah/cli,cpuguy83/cli,allencloud/cli,Zebrilee/cli,redpanda/cli,thaJeztah/cli,allencloud/cli,redpanda/cli,docker/cli,riyazdf/cli,e11137/cli,e11137/cli,cpuguy83/cli,riyazdf/cli,dnephin/cli,ashfall/cli