support `module-aliases-as-namespace` style

[agarwal]

Support OCaml's new module aliases as namespace feature, described here in the paragraph beginning "These weakened dependencies ...".

What should be done is:

• All file names should be prefixed with the project name.
• Each lib's sub-directory should have a single std.ml file.
• All ml and mli files in that directory other than std.ml should start with open Std, or perhaps better is to pass -open Std to ocaml.

This would be in addition to the Basic and Pack options as discussed in #16.

[agarwal]

This feature should be easier to implement now that we have codept.