Observerui

#4716 implementation of generic observer-stats UI for all mods. Includes a basic UI Editor to adjust information shown per mod per dropdown item. Includes shortcuts for dropdown menu in game settings.
This too could be merged into ColorBlockWidget by defining GetBorderColor and GetBorderThickness hooks.  This would also be useful in the lobby, where we could draw a border around the color block using the color at the dark end of the color ramp.