OPENDJ-1116 Introduce abstraction for the changelog DB

Removed ReplicationServerDomain.getReplicationServer() to follow the Law of Demeter: "Only talk to your immediate friends." to promote loose coupling.
Changed approxFirstMissingDate from Long object to long primitive.


ReplicationServerDomain.java:
Removed getReplicationServer().
Added getLocalRSMonitorInstanceName() and getLocalRSServerId().

*.java:
Used the newly added ReplicationServerDomain.getLocalRSMonitorInstanceName() and ReplicationServerDomain.getLocalRSServerId().

LightweightServerHandler.java:
Removed getLocalRSMonitorInstanceName().


MonitorMsg.java, MonitorData.java:
Changed firstMissingDate from Long object to long primitive.
Used StringBuilder in toString().

SynchronizationMsgTest.java
Changed approxFirstMissingDate from Long object to long primitive.
Extracted methods newList(), newSet(), getEntryAttributes(), assertAttributesEqual().
Used assertEquals() instead of assertTrue().