Differentiate preproduction/test sites in mapping

[ghalse]

The existing mapping code displays preproduction/test sites on the home page, but does not mark them differently. This leads users to expect working eduroam at those sites.

This pull request does two things:

1. it updates the existing marker to a higher resolution one (the original SVG being under CC0) to make the map display better; and
2. it introduces a new marker for preproduction/testing sites to make this clearer to end users.