Prototype a profile object.

Wrappers a JSON profile specification.

Adds a new dependency on json-glib-1.0.

Also adds a "Profiles" D-Bus interface to the service with a number of
methods for manipulating profiles locally:

  Add (String json_data)
  AddFile (String json_file)
  Get (String uid) -> (String json_data)
  List () -> (Array of [String] uids)

TODO: Require authorization for the Add() and AddFile() methods.
      We don't want non-privileged users adding their own profiles.