change default points_gaussian representation

[akaszynski]

This PR changes the default points_gaussian to use render_points_as_spheres=False. This is a bit more of a sensible default as emissive=False by default and it has no issues rendering on a white background.

Also moves colors.rst into a new directory and renames it to colors_table as sphinx was complaining about a recursive include locally despite clean builds. I'm not sure why it's not occuring in our builds, but I'd like to make sure this issue doesn't occur for others.

[codecov]

Codecov Report

Merging #3559 (0f52ea8) into main (e39c129) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #3559   +/-   ##
=======================================
  Coverage   95.16%   95.17%           
=======================================
  Files          83       83           
  Lines       18571    18571           
=======================================
+ Hits        17674    17675    +1     
+ Misses        897      896    -1