Creating a base inception style

I added three things to the base inception style.  They can be overridden, but without them, inception doesn't really work.

1) background-color.  Without this being set, you can see from one layer to the other.

2) box-sizing.  Without this the sizing math doesn't work out.

3) border.  It's debatable whether this is required, but without it, things look really confusing.