Refactor Solarized

Looks like for Solarized theme colors, I'm going to want access to the
actual colors as frozen brushes that can be easily shared. Solarized.cs
has been refactored into 3 classes to help with this:

Colors: Stores and exposes the 16 base colors.
Brushes: Stores and exposes 8 frozen accent brushes.
Theme: Stores and exposes 5 Themed brushes.

Usages have been updated. Also, since Solarized already exposed its
website as an info string, that string is now used for its About link.