[thedatahub.org] "Upload Data" should provide a nicer

[timmcnamara]

If someone who is not logged in clicks on "Upload Data", they are presented with

    Not authorized to upload files.

This is in emboldened red text. That is, the system is telling a user that they're doing something illegitimate, even though they're actually following an invitation from the main menu.

I propose two options for resolving this:

1. only display the "Upload Data" tab if someone is authorised to upload data
2. if someone isn't logged int, provide a nice welcome message thanking them for wanting to upload data, but we only allow registered users to do so

ENV: thedatahub.org, CKAN 1.4.2b

[rgrp]

invalid as things have changed and this has been fixed or obsoleted.