Add option to style all day events separately from other events

[raetha]

I tried to see if there was an existing class that seemed to cover all day events but it didn't appear so. They did get tracked as running events, which gets part way to my goal. That would just also capture the current active event, I believe.

My end goal is to change the background color of all day events to allow for easily skimming them for what they are.

Happy to test or assist in any way.