[Open Assets] Color selection for single player 6

• Restored savecolor functionality
  • This was broken since SRB2 version 2.2.11
• Added a "botcolor" command to change your partner bot's color
  • Previously, the bot always used the opposite color of yours
• Renamed the "forcecolor" command to "recolor"
  • I got annoyed by the constant "unknown command forecolor" and made it easier to type
• Updated the Radiant color with a completely new color ramp
  • The previous Radiant became redundant when Goldenrod was added to the vanilla game

• Renamed the custom color Ocean to Fountain (this avoids a name conflict with one of Neo Sonic's colors)
• Very minor correction to the color ramp of Breeze
• Added failsafe preventing duplicate freeslots
• Fixed a potential config loading error on non-Windows platforms
• Blocked the commands from being used in multiplayer