This is about refactoring the way the directory server chooses the 
replication server it will connect to. This also introduces a new 
(weighed) load balancing feature that spreads DS connections across the 
RSs, according to the RS weights defined by the administrator,

Issue 4343: https://opends.dev.java.net/issues/show_bug.cgi?id=4343

The commit includes necessary modifications for implementing what is 
described in this document:

https://www.opends.org/wiki/page/ReplicationServerSelection

There is a little "implementation" section in this document that 
explains some important stuff.

Also good to know for these code modifications:

- The topology info related to RSs and kept by the ReplicationBroker is 
now fully kept in a new map of a new ReplicationServerInfo bag class. 
This map is updated upon reception of a TopologyMsg.
- Protocol change: the TopologyMsg now includes the RS url in the RSInfo 
list
- The dynamic change of the weight of a RS triggers a new TopologyMsg 
being fired, to support dynamic change of weights and automatic topology 
re-connections
- SameGroupIdPoller thread has disappeared and its functionality is 
replaced by the mechanism that re-evaluates the more suitable RS (see 
section 5, in the document for more details)