Make the "continue scenario" button full size

The <a> is now the full size of the container (so that clicking anywhere
within the box continues the scenario), and the text is bold to draw
extra attention to it.
Trash Georgia on accordian titles
Remove blurry shadow from the sidebar
Tweak accordian / chart header title color
Make info/tutorial/add-chart buttons simpler

These are not so important for every-day use, and the borders,
gradients, and shadows can distract from the real purpose of the page.
Bye Georgia!
Add separator above scenario settings in menu
Slightly tweak title button colours
Simplify sidebar
last sidebar changes
Increase spacing around main content elements
Improve the sidebar demand icons

Remade most of them so that they're not so blurry around the edges.