Use country colors for graphs and maps; avoid duplicates

[MichaelMakesGames]

Closes #80

A few notes:

• This tries to avoid duplicates by darkening/lighting colors (shifting the v in hsv)
  • The actual resolved color of a country can change depending on what other countries exist in the DB, so game_id needs to passed in to get_color_vals
  • Country colors for a given game_id are cached. If any countries are created, the cache is cleared
• This tries to avoid grayscale colors by using the secondary color if the primary color has low saturation
• A minimum v is enforced for readability
• I needed to enhance the rust parser to understand the color value syntax (eg rgb { 1 2 3 }, hsv { 0.1 0.2 0.3 })