enabled fast resume for WP8 version
added FirstAddress to Bing FindLocationResponse
DownloadUrl also passes the WebResponse object and uses Deserialize that handles Json or Xml formats
LocationHelper.FindAddress first tries Google 2 times and if it fails then tries Bing 2 times
CityContextViewModel.GetAvailability2 didn't check if availability was assigned
StationViewModel.CheckAvailability didn't check if availability was assigned