Move \OCP to PSR-4

lib/base.php

lib/public/API.php

lib/public/App.php

lib/public/AutoloadNotAllowedException.php

lib/public/BackgroundJob.php

lib/public/Config.php

lib/public/Constants.php

lib/public/Contacts.php

lib/public/DB.php

lib/public/Defaults.php

lib/public/Files.php

lib/public/GroupInterface.php

lib/public/IAddressBook.php

lib/public/IAppConfig.php

lib/public/IAvatar.php

lib/public/IAvatarManager.php

lib/public/ICache.php

lib/public/ICacheFactory.php

lib/public/ICertificate.php

lib/public/ICertificateManager.php