add modules support

[gerau]

Partially closes #2.

This PR does several things:

• add the linearization_map field to Document so we can get info about functions from outside the given file.
• refactor Document: move functions that perform operations with SimplicityHL Functions inside the Document implementation, because it makes more sense and uses the new linearization_map.
• remove jet::documentation because we already moved the documentation inside the compiler itself.
• make the necessary changes to parsing and LSP functions to support multi-file architecture.

Right now, all LSP functions are working except for references, because we need to find a way to support references from modules to the files that use these modules. Also, I think multi-file support could be done better.

Draft for now, because it uses a custom fork of SimplicityHL with public visibility of DependencyMap and Module.