Add disclosure somewhere re how UI reports that there is no responsive data in the DB

One topic we discussed during today's jit.si meeting is how to report -- in the `Package details` page -- the fact that the VCIO DB has no responsive data for certain fields (e.g., `Non-vulnerable version` or `Fixed by` column). (This can be the case with other UI pages as well, e.g., the various tabs in the `Vulnerability details` page. And perhaps this will apply in some fashion to the API as well.)

In order to communicate as clearly as possible with users, we want to add a statement somewhere (perhaps the [Terms of Service](https://public.vulnerablecode.io/tos/)?) describing what we intend to communicate.

Please share your thoughts, suggestions and questions here.