Geojson support for hyperlinking

I am not suggesting you roll this in as yet, though it's a simple enough idea and easy enough to implement.
I couldnt get the url field to work, I am just linking to /BRK_NAME and expecting apache to sort that out, so that needs fixing. There may also be further generalisations for what to do with these geojsons that might make it a bit more interesting.
Suggestions most welcome on how this kind of functionality might be optionally included, or any other issues. We surely dont want to have all functionality anyone comes up with loaded by everybody no matter what. I am going to be cooking up loads of stuff, most of which will be of no interest to most but could be of some interest to some.