Add show bgp and show route commands, and clear bgp neighbor

[sha90w]

Added the following CLI commands:

show bgp summary
show bgp ipv4 summary
show bgp ipv6 summary
show bgp neighbor NEIGHBOR
show bgp neighbor NEIGHBOR received-routes
show bgp neighbor NEIGHBOR received-routes ipv4
show bgp neighbor NEIGHBOR received-routes ipv6
show bgp neighbor NEIGHBOR advertised-routes
show bgp neighbor NEIGHBOR advertised-routes ipv4
show bgp neighbor NEIGHBOR advertised-routes ipv6
show route
show route ipv4
show route ipv6
clear bgp neighbor

@rwestphal Please let me know if I should split the PR or adjust something

[rwestphal]

@sha90w Thank you. This is very much appreciated!

Really happy to test the new commands in one of my local BGP lab topologies:

holo# show bgp summary 
 Instance | Description | Neighbor | AS    | State       | Up/Down  | Pfx     | Trans. | MsgRcvd | MsgSent 
          |             |          |       |             |          | Rcd/Acc |        |         |  
----------+-------------+----------+-------+-------------+----------+---------+--------+---------+---------
 main     | -           | 10.0.1.2 | 65002 | established | 00:00:16 | 3 / 3   | 1      | 5       | 6 
 main     | -           | 10.0.2.4 | 65004 | established | 00:00:16 | 3 / 3   | 1      | 5       | 7 
 main     | -           | 10.0.3.5 | 65005 | established | 00:00:16 | 3 / 3   | 1      | 5       | 7 

holo# show bgp neighbor 10.0.1.2
BGP neighbor is 10.0.1.2, remote AS 65002, external link
 Description: -
  BGP version 4, remote router ID 2.2.2.2
  Hold time is 90, keepalive interval is 30 seconds
  BGP state is established, up for 00:00:33
  Number of transitions to established: 1
  Neighbor Capabilities:
    Options: <mp-bgp asn32 route-refresh>

  Address families configured: ipv4-unicast

  Message Statistics:
                                    Sent       Rcvd
    Updates:                           4          3
    Notifications:                     0          0
    Total messages:                    7          6

  Prefix Statistics:
                               Sent       Rcvd  Installed
    ipv4-unicast                  4          3          3

 Local AS is 65001, local router ID 1.1.1.1
 Local TCP address is 10.0.1.1, local port is 35914
 Remote TCP address is 10.0.1.2, remote port is 179

holo# show bgp neighbor 10.0.1.2 advertised-routes 

Address family: ipv4-unicast
              Prefix              NextHop   MED LocalPref AS Path
          1.1.1.1/32                    -     -         -  ?
          4.4.4.4/32             10.0.2.4     -         - 65004 ?
          5.5.5.5/32             10.0.3.5     -         - 65005 ?
          6.6.6.6/32             10.0.2.4     -         - 65004 65006 ?
holo# show bgp neighbor 10.0.1.2 received-routes 

Address family: ipv4-unicast
              Prefix              NextHop   MED LocalPref AS Path
          2.2.2.2/32             10.0.1.2     -         - 65002 ?
          3.3.3.3/32             10.0.1.2     -         - 65002 65003 ?
          6.6.6.6/32             10.0.1.2     -         - 65002 65003 65006 ?

holo# show route ipv4 
1.1.1.1/32           *[Direct/0] 00:01:11
                     >  via lo
2.2.2.2/32           *[BGP/20] 00:01:07
                     >  to 10.0.1.2
3.3.3.3/32           *[BGP/20] 00:01:06
                     >  to 10.0.1.2
4.4.4.4/32           *[BGP/20] 00:01:06
                     >  to 10.0.2.4
5.5.5.5/32           *[BGP/20] 00:01:07
                     >  to 10.0.3.5
6.6.6.6/32           *[BGP/20] 00:01:06
10.0.1.0/24          *[Direct/0] 00:01:11
                     >  via eth-rt2
10.0.2.0/24          *[Direct/0] 00:01:11
                     >  via eth-rt4
10.0.3.0/24          *[Direct/0] 00:01:11
                     >  via eth-rt5