Support accepting and displaying table names in OVS tools.

Support accepting and displaying table names in OVS tools.

OpenFlow has little-known support for naming tables.  Open vSwitch has
supported table names for ages, but it has never used or displayed them
outside of commands dedicated to table manipulation.  This commit adds
support for table names in ovs-ofctl.  When a table has a name, it displays
that name in flows and actions, so that, for example, the following:
    table=1, arp, actions=resubmit(,2)
might become:
    table=ingress_acl, arp, actions=resubmit(,mac_learning)
given appropriately named tables.

For backward compatibility, only interactive ovs-ofctl commands by default
display table names; to display them in scripts, use the new --names
option.

This feature was inspired by a talk that Kei Nohguchi presented at Open
vSwitch 2017 Fall Conference.

CC: Kei Nohguchi <kei@nohguchi.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Mark Michelson <mmichels@redhat.com>
Reviewed-by: Yifeng Sun <pkusunyifeng@gmail.com>