OVSDriver: replace kflow->flows with kflow->stats_ptrs

We have to track stats on more than just OpenFlow flows - table, group, and
meter stats, for example. Since we were only using the flows array for stats
purposes replace it with an array of pointers to struct ind_ovs_flow_stats.
OVSDriver: add table matched stats to kflow->stats_ptrs

Retrieving the table stats from the datapath will not work with multiple
tables.

Once we have multiple tables, each one that a kflow traverses will have its
matched or missed stats struct in the stats_ptr array.
OVSDriver: move per-table state into struct ind_ovs_table
OVSDriver: send all tables in table_stats_reply
OVSDriver: insert flow into table based on table_id
update indigo to f71516e9b53aadf18a0d974c9d3582c7160ea603
OVSDriver: compute actions in ind_ovs_kflow_add

The previous code copied the actions used to execute the packet in the upcall
handler into the BH request. This was incorrect because the flowtable could
change between the request being enqueued in an upcall thread and handled in
the main thread.

This change moves the flowtable lookup and action translation into
ind_ovs_kflow_add. This is now symmetric with ind_ovs_kflow_invalidate.
OVSDriver: move actions nlattr creation out of ind_ovs_translate_actions

Most callsites needed to use nlmsg_find_attr to find the attribute afterwards
anyway.

Unfortunately we have to create a wrapper for nla_nest_end to make sure it
doesn't delete the attribute if it would be empty.
OVSDriver: remove support for OFPP_TABLE

Combining arbitrary packet-out actions with OFPP_TABLE is difficult. Instead of
doing the work to support this in the new multi-table pipeline I'm ripping it
out.

If we want to support OFPP_TABLE in the future we could consider doing it for a
very restricted set of packet-out actions (single output to OFPP_TABLE).
OVSDriver: replace ind_ovs_lookup_flow with ind_ovs_fwd_process

This replaces the single-flow result with a new struct ind_ovs_fwd_result which
contains the actions and stats pointers.
OVSDriver: populate kflow->actions_len

Bug found by valgrind.
OVSDriver: implement goto_table instruction

Also bump the number of tables to 16.
Merge remote-tracking branch 'origin/master' into pipeline3
Merge into master from pull request #49:
multi-table pipeline (https://github.com/floodlight/ivs/pull/49)