mdg:geolocation ~ position won't be watched / asked again after error

When onError is triggered we should set `watchingPosition` to false, so then we can call startWatchingPosition again ( and try to fetch the location again ).

At the moment if i received a TIMEOUT error, it doesn't retry and it seems that the app will only update the position if you refresh the page, when you could actually just call watchPosition again and get onPosition callback called.

Inspect the geolocation package's onError handling and the watchingPosition state used by startWatchingPosition. Confirm that a timeout or other error allows startWatchingPosition to be called again and that a later onPosition callback updates the location; pull request #87 is already open for this issue.

Written by the indexing model from the issue text.