OPENDJ-960 (CR-1858) Rest2LDAP - Validate http-config.json file 


Enhanced JsonValue by adding a record/verify mode for key accesses.
Client code must call record recordKeyAccesses() to verifyAllKeysAccessed().
When an unaccessed key exists, a JsonException will be thrown and all unaccessed keys will be reported (unaccessed keys located under other unaccessed keys are not reported to reduce noise).


Rest2LDAP.java, Rest2LDAPAuthnFilter.java, Rest2LDAPConnectionFactoryProvider.java:
Called recordKeyAccesses() before accessing the keys, then verifyAllKeysAccessed() to verify all the keys have been accessed after we are done with the JSON config.