This change updates the project structure to become flattened.
Previously, the simulator, frontend and API each lived into their own
directory.

With this change, all modules of the project live in the top-level
directory of the repository. This should improve discoverability of
modules of the project.

This change updates the frontend such that metrics are now shown by
their full name instead of a code.

This change adds more models to the unit specifications in order to be
able to build more advanced topologies.