Added an option to add a unique identifier to some formats.

Module.php

config/module.config.php

config/module.ini

src/Form/ConfigForm.php

src/OaiPmh/Metadata/AbstractMetadata.php

src/OaiPmh/Metadata/Mods.php

src/OaiPmh/Metadata/OaiDc.php

src/Service/OaiPmh/Metadata/CdwaLiteFactory.php

src/Service/OaiPmh/Metadata/MetsFactory.php

src/Service/OaiPmh/Metadata/ModsFactory.php

src/Service/OaiPmh/Metadata/OaiDcFactory.php