Built in Closure plugin into loader

[Arthur Buldauskas]

Goal

Make it easy to use .walt files

Overview

A user should not have to pass in an importsObject with a closure plugin by default.

Acceptance Criteria

• Add a compile-and-link option/function to the compiler
• Add closure plugin handling to the loader
• Write a test

[Arthur Buldauskas]

A plugin system from #133 should be utilized instead.