bgpd: add terse display option on show bgp summary

bgpd: add terse display option on show bgp summary

Add a terse option to show bgp summary to shorten output.

Do not show the following information about the BGP
instances: the number of RIB entries, the table version and the used memory.
The "terse" option can be used in combination with the "remote-as", "neighbor",
"failed" and "established" filters, and with the "wide" option as well.

Before patch:

ubuntu# show bgp summary remote-as 123456
IPv4 Unicast Summary (VRF default):
BGP router identifier X.X.X.X, local AS number XXX vrf-id 0
BGP table version 0
RIB entries 3, using 552 bytes of memory
Peers 5, using 3635 KiB of memory

Neighbor        V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd   PfxSnt Desc
10.200.200.2    4     123456     81432         4        0 56092    0 00:00:13       572106        0 N/A

Displayed neighbors 1
Total number of neighbors 4

IPv6 Unicast Summary (VRF default):
BGP router identifier X.X.X.X, local AS number XXX vrf-id 0
BGP table version 0
RIB entries 3, using 552 bytes of memory
Peers 5, using 3635 KiB of memory

Neighbor        V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd   PfxSnt Desc
% No matching neighbor

Total number of neighbors 5

After patch:

ubuntu# show bgp summary remote-as 123456 terse
IPv4 Unicast Summary (VRF default):
BGP router identifier X.X.X.X, local AS number XXX vrf-id 0

Neighbor        V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd   PfxSnt Desc
10.200.200.2    4     123456     81432         4        0 56092    0 00:00:13       572106        0 N/A

Displayed neighbors 1
Total number of neighbors 4

IPv6 Unicast Summary (VRF default):
BGP router identifier X.X.X.X, local AS number XXX vrf-id 1

% No matching neighbor

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>