Calls the API for fenced station only when data is outside the fence
Calls the API for fenced station only when data is outside the fence

We track the biggest fence we have obtained data for, and we only call
the API to get the station when we move outside that fence. If we zoom
in and move inside the biggest fence the API is not called, so we save
calls and renderings.
SeGarVi/moveon-web,SeGarVi/moveon-web,SeGarVi/moveon-web