ospfd: Add prefix-list filtering of OSPF neighbors on OSPF interface

ospfd: Add prefix-list filtering of OSPF neighbors on OSPF interface

This commit adds the capabiity to filter OSPF neighbors using a
prefix-list with rules matching the neighbor's IP source address.
Configuration, filtering, immediate neighbor pruning, topo-tests,
and documentation are included. The command is:

     ip ospf neighbor-filter <prefix-list> [A.B.C.D]

Signed-off-by: Acee Lindem <acee@lindem.com>