Order the API sections is a bit confusing

[marcoscaceres]

The order of the spec's APIs is somewhat confusing. It should really start with the extensions to the Navigator object, as that gives the reader a better idea as to how the whole API is supposed to be used.

So, I would put them in this order:

1. Extensions to Navigator
2. ApplicationRegistry
3. ApplicationManagement
4. Application.
5. DownloadRequest (though with futures, this no longer applies).

Also, this whole section (Application Management) should probably be better grouped into a "feature". That is, this feature/API only becomes available if requested via the manifest and if the runtime grants it access. As such, this could be grouped much more nicely into it's own spec and spun off.