Download files in codename directories
Name zip with journalist_filename() instead of journalist_designation

Instead of naming the generated zip file with the journalist_designation
which can contain spaces, it's probably better to use the output of
journalist_filename() which removes spaces explicitly, and aims to be
filesystem safe.
Add test checking zipfile contains correct user directories
Merge pull request #593 from DonnchaC/user-directories-in-zips

Add directory with source's codename to the zip files.