Add DocumentViewer, with dependencies.
BGeolocation: make it work with the actual API.

* It seems openbmap is using a variation of the API that's not
compatible with what other providers use.
* Fix a ";" instead of "," in the JSON request. We should get a
BJsonBuilder to avoid such silly errors
* Improve indenting of the request to ease readability.
* Parse the latitude and longitude as doubles, not strings.

This was tested against Mozilla Location Services and I get accurate
results (withing a few hundred meters). However I'm not sure how to
share the MLS API key safely so it is used only in Haiku, I will discuss
this with the MLS team.