Build failure caused by unsafe URL-File conversion in KMLMapTransformer

The new behaviour and expanded unit test coverage introduced in r14469 by GEOS-3994 causes the build to fail in a path with spaces. (The broken code existed before; these changes in GEOS-3994 found it.)

While determining the location of a symboliser graphic, we have:

File file = new File(graphic.getLocation().getFile());

This is unsafe because it does not unescape URL encoded characters such as spaces. If the graphic is present in a path with spaces, the resulting file does not exist. The solution is to replace this with:

File file = DataUtilities.urlToFile(graphic.getLocation());