Pluploader Plugin Fix

In some configurations with plugin PLUPLOAD files can be selected, upload starts and finishes without problem. After the upload, however, the files do not appear in Pydio and cannot be found on the filesystem. Instead an error "failed to open stream: Is a Directory in class.fsAccessWrapper.php" is logged.

Obviously both plugins uploader.html and uploader.plupload use the same action name “upload_chunks_unify”, so the action name needs to be changed to a new name like "upload_chunks_unify_plupload".

See also forum discussion https://pyd.io/f/topic/plupload-not-storing-files-beta-5-3-3