Front page theme

[MegaKeegMan]

See: https://docs.google.com/presentation/d/1A6hYPYsI-EzGrOtOUBF37MD0uHweKGqfQJXkCZzo6VM/edit#slide=id.g2bac27af0c5_0_2

It is noteworthy that the display of some front page content depends on whether the visitor is logged in or not.

[MegaKeegMan]

Need to consider how we want to utilize different regions:

• the slideshow could go into the content region, but the sidebar there may differ from the sidebar on different pages, so we will likely need a dedicated banner sidebar
• the Explore a Project block has a grey background that spans the width of the screen, and so it would be good to have a dedicated region that provides that wide grey background

[MegaKeegMan]

No longer going the route of requiring full width "regions" in order to have full width elements, per the above commit