Binder environment repository for plenoptic. Inspired by this thread, this repository is an "environment repository" which has all the various configuration required to define the environment Binder will build. The main plenoptic repository is then used as the "content repository", pulled into the built environment on launch. This separation allows a more consistent built repository (so we rebuild less often) and also separates out the (distracting) configuration files from the main repository.