Improve and fix bugs with drawer

@peter-riggs If you would like to code review this... 

I found there were some bugs with the drawer which I have fixed here. They were:
* The items were too small to click on a real device.
* There was a crash when selecting a state after changing orientation
* The stations list did not remember state selections
* the stations list would 'double up' (the fragment would be shown twice, potentially with different lists) if a state was selected from the drawer while on the graph and then the back button pressed.