Polling the whole dataset is inneficient

[mbanders]

The dashboard polls for data, asking for all the data every few seconds. Really it should just ask for all the data once, and then simply wait for new data on a websocket.

Specifically: The dashboard (src/views/Dashboard.vue), every few seconds, calls the function loadStations in the file src/store/store.js. Instead of doing this, it would be nice to only update when there's new data.