Remove font customizations

* Should respect whatever font the user has set.
  (“Respect the user’s settings by always using the system font, sizes, and colors.” http://msdn.microsoft.com/en-us/library/windows/desktop/aa511282.aspx)
* Courier looks odd and it’s too thin to see (a11y issue #4082).

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@davidsansome: I’m experimenting with a clockface-like font that I’m creating in FontForge, BTW.