[update] Don't start Geoclue satellite providers until necessary.

Cherry picked commit 642098c893be76ad9c049910661059bb926dc6d6
from upstream.
[update] Set default preferred positioning methods for Geoclue position source.

Cherry picked commit 7e0283264806e16fc7373e1c05588bddce6c79a8
from upstream.
[update] Fix incorrect accuracy values reported by Geoclue plugin.

Cherry picked commit 5708dfcc80ac4eb029bab6af9b9fbee148da0786
from upstream.
Merge pull request #21 from amccarthy/master

Cherry picked updates from upstream.