Promotional features for executive offices

Tracker: https://www.pivotaltracker.com/story/show/46261745

Executive offices can now have any number of "Promotional features", which are made up of up-to 3 "Promotional feature items" (or 2 if one is double-width). Each item consists of an image, some text an optional title (plus link) and a number of additional links (up-to 6).

This is best illustrated in the visuals: https://www.pivotaltracker.com/resource/download/17473267

For this first pass, there is no facility to sort the promotional features, and they will be rendered in the order they have been added, clearing onto new rows as appropriate depending on the space available.