Move lib/ to PSR-4

apps/federatedfilesharing/lib/Notifier.php

apps/files_sharing/lib/Activity.php

apps/files_sharing/lib/Cache.php

apps/files_sharing/lib/Capabilities.php

...iles_sharing/lib/Controllers/ExternalSharesController.php

apps/files_sharing/lib/Controllers/ShareController.php

apps/files_sharing/lib/Exceptions/BrokenPath.php

apps/files_sharing/lib/Exceptions/S2SException.php

apps/files_sharing/lib/ExpireSharesJob.php

apps/files_sharing/lib/External/Cache.php

apps/files_sharing/lib/External/Manager.php

apps/files_sharing/lib/External/Mount.php

apps/files_sharing/lib/External/MountProvider.php

apps/files_sharing/lib/External/Scanner.php

apps/files_sharing/lib/External/Storage.php

apps/files_sharing/lib/Helper.php

apps/files_sharing/lib/Hooks.php

apps/files_sharing/lib/ISharedStorage.php

apps/files_sharing/lib/Maintainer.php

apps/files_sharing/lib/Middleware/SharingCheckMiddleware.php