OPENDJ-2819 Setup error (NPE)

Fixed a collection of problems that prevented the server to start.

Installer.java:
Remove last references of the --configClass CLI option.

DirectoryServer.java:
Added back missing configuration initialization and incorrect
finalization.

DeleteBaseDNAndBackendTask.java, ConfigureDS:
Do a deep copy of the unmodifiable config entry which has unmodifiable
attributes too.

HostPort.java:
Changed class so it accepts unspecified hostname and port (null and 0).

ControlPanelInfo.java:
Removed references to ConfigFileHandler.