The Solarized theme doesn't work well on light themes. (Light/dark have
identical palettes, but the foreground/background colors are different
and greys obviously get used differently.)
This commit makes the 'solarized' theme use the foreground color instead
of '250' and use the average of base00 and base0 for DiskBar. (These
greys are already close to 50%.)
This commit also adds two 16-color themes utilizing the extra violet/
orange colors, and uses the appropriate grey color for DiskBar.
