Dismissable banners

[fenekku]

Is your feature request related to a problem? Please describe.

In our instance prior to invenio-banners, we had a very simplistic approach to create banners, but we had it such that they were dismissable. Once dismissed, for the length of the user's session, the banner wouldn't re-appear. We would like a similar functionality (potentially an option in the admin panel).

Describe the solution you'd like

Use the g.session and some ajax. That's what we've done.

Additional context

I will check with our librarians how high this ranks.