Add `ChatColor` enum

This a general class (perhaps better referred to as an `enum`) that handles formatting and colors. Documentation is convoluted and a bit sparse, but I think it's sufficient for now.

Note: I created a new package `org.spongepowered.api.chat` for it, because I wasn't sure where to put the file.
@kenzierocks https://github.com/Bukkit/Bukkit/blob/master/src/main/java/org/bukkit/ChatColor.java#L233 If it found the color, it replaced, otherwise it left the text as-is.