warn if position watcher called while Simulator not running
stop watching geolocation before closing client
Merge pull request #640 from mykmelez/client-null

prevent `this._remote is null` exception in position watcher (fix #579)
update Gaia to 2013-06-19 tip of v1-train
update B2G to 2013-06-19 tip of b2g18 branch
Merge pull request #646 from mykmelez/update-b2g-gaia

update B2G/Gaia to 2013-06-19 tips of b2g18/v1-train branches