Update SearchViewModel with additional logic

- Removed service tests in SearchViewModel constructor
- Changed SearchText property to run the Search function when set
- Changed Station search results from List to ObservableCollection
- Completed ExecuteSelectStationCommand to change IsFollowed property to
true if Station is selected and false if already true
- Implemented GetStations method in LocalDbService using lambda
expression
Merge branch 'feature/gtfs-realtime'