Changes in Station and StationActivity

- Added overriding of Object#equals and Object#hashCode in Station
- Added overriding of Activity#onStart in StationActivity
- Moved some behaviour from StationActivity#onCreate to
StationActivity#onStart
- Moved refreshing process from StationActivity#onCreate to
StationActivity#refreshStationData (to further reuse it in
StationActivity#onStart)

(+ a syntactic change in MainActivity)