Support multiple elections in the API and routes

[rkorsak]

We expect to be able to handle multiple elections in the future, and the API/routing layer will need a breaking change to support that.

We should:

1. Modify the DataAccess interface with a getElections method instead of getElectionDescription
2. Modify the routes so that the election ID is part of the route
3. Load the elections at the root of the app and redirect to the first election in the array once it loads