Module system

[thinker227]

Implement a system for importing and exporting functions from different files/modules.

A couple alternatives for a basic syntax:

from "./path/to/module" import {a, b, c}

// Very function-like
import ./path/to/module(a, b, c);

// Javascript-y
export func f() => ...;

// Function-like
export(f);
func f() => ...;

Additionally it would be somewhat nice to be able to import/export things as aliases.

(this issue is a heavy work in progress, more research should be done on how to implement a decent module system)