Add basic test harness

[pittst3r]

Motivation

We want to have a test harness in this project, obviously. And we want to dogfood BigTest to put it to the test.

Approach

• Split frontend and backend into separate directories
• Install BigTest

To-do

• [x] Cut a BigTest release and update the versions in this project so that it will actually work
• [ ] ~Make the path to the configuration file configurable through a CLI option so that we can have different configs for frontend and backend~ nodedriver is not ready, so we will not be testing the backend with BigTest yet
• [ ] CI

[pittst3r]

Gonna merge. We can add CI and iterate on project structure in future PRs.