OPENDJ-1116 Introduce abstraction for the changelog DB

Hid low level JE's DatabaseException and ReplicationDBException from replication higher level code. They have been replaced by the newly created ChangelogException.

Tidied up the exception handling by throwing or catching more specific exceptions.
Moved some code to protect them with try / catch.
Adding a few catch for specific handling of ChangelogException.
Threw ChangelogException instead of Exception.
Added handleUnexpectedDatabaseException() methods.

ReplicationDBException.java: REMOVED (now useless)

replication*.properties:
Removed ERR_COULD_NOT_INITIALIZE_DB, not adding anything to ERR_COULD_NOT_READ_DB.

Removed "this." from member method invocations.
Used Integer.parseInt().
Used StaticUtils.close().