When origin is playground, create user/interview-specific runtime_config vals

[plocket]

Right now, ALKilnInThePlayground relies on one runtime_config globally to find the artifacts folder for the test. That means two users shouldn't test at the same time. In fact, only one test should run at a time. Either each user/interview combo should have a runtime_config of its own or the runtime_config obj should have a key for each user/interview combo. It can be deleted when the tests are done (with a catch for situations where runtime_config hasn't been created).

Also, explore how to put runtime_config into the root of the docker container (or some other more cleanable (or permanent) location).