Interface layer between the protocols and the shell

The protocol-environment is a two-sided component sitting between the shell and the protocols.

On one side, it provides a restricted typing environment to compile the protocols against. This is a series of modules which replace the standard library of OCaml. These modules purposefully omit many functionalities, thus preventing the protocols from, say, directly writing to disk.

On the other side, it provides the shell with specific call-sites in the protocols. These are the only entry-points into the otherwise black-box protocols.