Add rudimentary location support

This is an ***untested*** proof-of-concept for how #59 could get handled. I didn't dig too much into how the server is actually wired up to the `UBWindow`, so there could be an issue with this particular approach where the widgets are loading before the location data is injected to the webview's `window`.

It also probably makes more sense to have the location delegate use `callWebScriptMethod:withArguments:` when the location changes, so the script could actually respond to the changes. This probably just needs to call `refresh`, or there could be a more explicit function that gets called. 

Happy to spend more time on this if it's something you think would make it in. 
This could also be left up to the widget to manage, which probably makes more sense.