Format in the name of the downloaded ZIP
When the user downloads several files (both from a search or from the shelf), he can choose between TEI and TXT. When the ZIP files is downloaded, it normally has the name of the first work downloaded, for example "faust_etc.zip". In the name of the zip, it should be contained the format chosed, i.e. "tei_faust_etc.zip" or "txt_faust_etc.zip".