Add Bolivia national shields

[whubsch]

This pull requests adds road shields for Bolivia's national route network. I can't find any evidence that these shields are used on the ground, but they are used in cartographic representations of the road network. National legislation also outlines designs for departmental and municipal route shields (see below), but I can't find any evidence that those are used in any context.

I've chosen just to reuse the green US interstate business route shield for simplicity's sake.

localhost link

departmental map of Oruro

[quincylvania]

It seems like the US route shield would be a better fit than the interstate shield? There is a function to set the color without adding another sprite.