odp-util: add verbose mode for displaying dp flow.

odp-util: add verbose mode for displaying dp flow.

When verbose mode tuned on, all dp flow fields described by the netlink
attributes are displayed, including fully wildcarded attributes.
Otherwise, the fully wildcarded attributes are omitted for brevity.

Added -m option to "ovs-dpctl dump-flows" to enable verbose mode. It is
off by default.

Signed-off-by: Andy Zhou <azhou@nicira.com>
[blp@nicira.com added documentation]
Signed-off-by: Ben Pfaff <blp@nicira.com>