Make sure artwork does not appear behind text

[joemull]

Fixes #242.

The strategy here is to create mostly invisible backgrounds that have the effect of erasing artwork that rolls behind text.

I went through all the custom templates to check for cases where this can happen and made changes. Here are some examples:

[StephDriver]

Testing and Observations

This looks great. I particularly like the naming of the classes using clock points.

• I can't find anything using pointing-8-oclock I assume that is there for completeness?

Otherwise I've reviewed one of each of the class examples.

• I am unsure about the use of pointing-10-oclock on the olh-award template - this looks odd with the triangle being parallel along one edge and almost but not along the other. For me this is jarring.

• Similarly, I am unsure about the angle used on the News page:
  Great at this size:

But this is the 100% zoom version:

Contrast that with the Internships page, where the angle of the background works well at multiple widths / zoom.

In Conclusion:

• I like the solution.
• I like the naming of the class.
• I think the choice of which class in which location may need a bit more thought. And after that, some documentation or guidance for future use as to how to chose which shape to use.