188071551 locations setup

[bacalj]

This adds the maintenance of an array of locations.

Locations are potentially updated on three events:

1. Get data button
2. Clear data button
3. CODAP-side deletion of cases

Locations are used to

1. check if we already have data for a given location
2. in an upcoming feature, populate a list of existing locations that can be selected to move lat/long in sim

[pjanik]

Looks great, thanks 👍

[pjanik]

Is the idea here to have something like a unique ID/key that can be easily compared? It's a pretty cool idea. However, I think I'll need a helper function like locationsEqual = (a, b) => a.lat === b.lat && a.long === b.long to check if a given lat/long matches any option in the dropdown. Then we could probably skip storing this derived property. This equality helper should probably be universal throughout the whole app. Alternatively, another option could be to generate this ID/key from the lat/long pair and compare the result. But it's pretty minor dilemma. 😉