Add iof:get_table_features, with sensible formatting

[legoscia]

Just dumping the response to the console doesn't make sense, as there's
lots of it, and much of it is almost identical. Attempt to present the
data in a compact but still fairly complete manner, by identifying
unique values for the various feature lists and summarising them as
footnotes.

It's recommended to run iof:debug(off) before requesting table features,
since otherwise all the data will be written to the console anyway.

Sample output from LINC:

([email protected])27> iof:get_table_features().
Id  Table name                       Max entries Instr NextTab WrAct ApAct Match Wild  WrSet ApSet
  0 Flow Table 0x00                  16777216    {1}   1-254   {3}   {3}   {2}   {2}   {2}   {2}  
  1 Flow Table 0x01                  16777216    {1}   2-254   {3}   {3}   {2}   {2}   {2}   {2}  
[...]
252 Flow Table 0xfc                  16777216    {1}   253-254 {3}   {3}   {2}   {2}   {2}   {2}  
253 Flow Table 0xfd                  16777216    {1}   254     {3}   {3}   {2}   {2}   {2}   {2}  
254 Flow Table 0xfe                  16777216    {1}   none    {3}   {3}   {2}   {2}   {2}   {2}  

{1}: [goto_table,write_metadata,write_actions,apply_actions,clear_actions,
      meter]
{2}: [in_port,metadata,eth_dst,eth_src,eth_type,vlan_vid,vlan_pcp,ip_dscp,
      ip_ecn,ip_proto,ipv4_src,ipv4_dst,tcp_src,tcp_dst,udp_src,udp_dst,
      sctp_src,sctp_dst,icmpv4_type,icmpv4_code,arp_op,arp_spa,arp_tpa,
      arp_sha,arp_tha,ipv6_src,ipv6_dst,ipv6_flabel,icmpv6_type,icmpv6_code,
      ipv6_nd_target,ipv6_nd_sll,ipv6_nd_tll,mpls_label,mpls_tc,mpls_bos,
      pbb_isid]
{3}: [output,group,set_queue,set_mpls_ttl,dec_mpls_ttl,set_nw_ttl,dec_nw_ttl,
      copy_ttl_out,copy_ttl_in,push_vlan,pop_vlan,push_mpls,pop_mpls,push_pbb,
      pop_pbb,set_field]