Display real Collections on MyGiza landing page

[npicardo]

MyGiza landing page (http://giza.fas.harvard.edu/mygiza/) has static image placeholders from design to indicate Collections that can selected by users.

Once Collections are functional, active examples should replace the placeholder

stills.

[lukehollis]

Looks great! I think we need the image uploads working to be able to do this effectively, but I can at least start templating these to be connected with the database.