Checkpoint commit for OPENDJ-1206 : Create a new ReplicationBackend/ChangelogBackend 
 to support cn=changelog

* Implement checking of CHANGELOG_READ Privilege
* Implement 2 more tests for changelog backend. 
   Tests are still disabled (until changelog backend is activated in code).

* ChangelogBackend.java: 
 - add new method checkChangelogReadPrivilege() to check CHANGELOG_READ
  privilege
 
* ChangelogBackendTestCase.java: 
 - implement searchInCookieModeAfterDomainIsRemoved test
 - implement searchInCookieModeOnTwoSuffixesWithPrivateBackend test