OPENDJ-1134 (CR-2338) Introduce a class in replication for encapsulating host+port combinations

HostPort.java:
Improved javadocs.
Improved host normalization for and used remote IP addresses for remote hosts (complies with code from ReplicationServer.java.disconnectRemovedReplicationServers()).
Renamed normalizedHost() tpo normalizeHost().
Removed trimming for serverURLs.
In valueOf(), added a special case to reject unbracketed IPV6 addresses.
Extracted constant LOCALHOST to avoid typos.
Reworked the code from isLocalAddress(), equals(), hashCode().

HostPortTest.java:
Reworked some tests.
Added new tests.