Add support for module hierarchies

[oubiwann]

Copied from the 2015 ticket in the old repo: lfe-rebar3/compile#4

Note that this is not true package support, since Erlang/LFE don't have such a concept.

Instead, this is about finding modules in a directory structure and creating a beam file name that is composed of the path elements of the module files parent directories.

This will mean that you can have a path structure like src/a/b/c/d.lfe and, once compiled, there would be a .beam file in ./ebin created with the name a.b.c.d.beam. Calling this module's functions from LFE code would be done in the usual manner: (a.b.c.d:some-func ...). The onus will of course be on the developer to ensure that the module is given the proper name: (defmodule a.b.c.d ...).

[oubiwann]

FYIW, this is exactly what the Clojerl project did.

[oubiwann]

Added in #38.