Remove data and zip archive access on landing page to non-authenticated (i.e., public) users

[servilla]

Remove data and zip archive access on the data package landing page to non-authenticated (i.e., public) users, complying with changes to PASTA service method authorization (see here: PASTAplus/PASTA#153). The landing page should display a message to the user that login/sign-on is required to download data or the zip archive.