More accurate color handling.

1. Instead of using the specified color for the top of the cap, and then
darkening the side, I use the specified color for the sides of the cap,
and then lighten the top.
-- All swatches were sampled from the smooth part of the color chips...
and the smooth is usually present on the *side* of the caps, not the
top.
-- The top of the caps usually has a matte-finish, which is visibly
lighter than the smooth finish.

2. Lighten the color in LAB-space, instead of in RGB-space.
-- results in better appearance for the light colors

3. Tweaked the gradients for DSA and DCS.

4. Updated existing sample layouts to use SP color values.
-- Deleted old/unloved sample layouts.
-- Darkened the Stealth-Black layout to match other changes.

5. Changed the default keycap color from #eeeeee --> #cccccc
-- Relative appearance is similar between old & new versions.