Allow download of station data

[tomLandry]

Station data can now be seen on map and in graphs, in the portal. As discussed in #72 there is a station downloader app available that can be integrated to the portal.

[dvdkamp]

@habitatseven, I've included some comments in the bug and issue tracker: https://docs.google.com/spreadsheets/d/1hZBA8MeYOL-26SlimyxdWKN9kKtNA_2yUnJdwIUzcPo/edit#gid=133082259 regarding this page. All non-high priority