OPENDJ-1908: Apply best practices and optimize search filters.

OPENDJ-1666 PR-19 CREST-3.0.0 Migration Design changes overview: * Make the code compiling against CREST-3.0.0 * Implement rest2ldap servlet and Http connection handler as a CHF filter/handler chain * Move all of the functionality out of the opendj-rest2ldap-servlet module and into the opendj-rest2ldap module, since it doesn't require Servlet - Servlet integration is provided by CHF. * Create an Ldap Http Handler which is shared by both rest2ldap servlet and httpConnectionHandler * Remove Rest2LdapContextFactory because the authn filter and handler can communicate directly via Context objects rather than using Servlet "attributes". * Rename Context to RequestState Detailed changes performed: Files which has been mostly modified: * org.opends.server.protocols.http.CollectClientsConnectionFilter * org.forgerock.opendj.rest2ldap.LDAPCollectionResourceProvider * org.forgerock.opendj.rest2ldap.ReferenceAttributeMapper Other changes are mostly minor, they just ensure that code compile against CREST-3.0.0.