OPENDJ-1116 Introduce abstraction for the changelog DB

Moved all JE changelog related classes to the new package org.opends.server.replication.server.changelog.je



DbHandler.java, DraftCNData.java, DraftCNDB.java, DraftCNDbHandler.java, DraftCNDbIterator.java, JEReplicationIterator.java, package-info.java, ReplicationData.java, ReplicationDB.java, ReplicationDbEnv.java, ReplicationDraftCNKey.java, DbHandlerTest.java, DraftCNDbHandlerTest.java:
Moved to package org.opends.server.replication.server.changelog.je

ReplicationServer.java:
Updated the imports.
Made getTrimAge() public.
Removed use of "this" from method invocation.
Moved handleUnexpectedChangelogException() to ReplicationDbEnv.

DraftCNDB.java, ReplicationDB.java:
Moved handleUnexpectedDatabaseException() to ReplicationDbEnv.

ReplicationDbEnv.java:
Moved handleUnexpectedChangelogException() here from ReplicationServer, and renamed it to shutdownOnException().
Moved handleUnexpectedDatabaseException() here from DraftCNDB and ReplicationDB, and renamed it to shutdownOnException().

ECLServerHandler.java, ReplicationServerDomain.java, ExternalChangeLogTest.java:
Updated the imports.