Add persistance

[xmclark]

There needs to be a pattern for creating routes that interact with our data.

We don't have many restrictions on the technology for our persistence layer. Home servers have a mixture of normal entity records and event sources. It does not need to be high performance right now.

We can optimize for developer experience and ease of use for now, and optimize later (maybe swap out database technologies).

[xmclark]

#19 adds some basic support for sqlite with diesel. This approach should be acceptable for now.

That PR does not add a way to make integration tests but we may be able to add them later. See these links:
https://github.com/actix/actix-website/blob/master/content/docs/testing.md#integration-tests
https://doc.rust-lang.org/rust-by-example/testing/integration_testing.html