Samepack

Finally fixed the global import bug in which if two constructs of the same name were exported, one would override the other.

The ``as`` syntax and the ``* as`` syntax are supported in imports.

Add module exection: ``python3 -m samepack`` works as an alternative to ``same``

Bug fixes

A bundle can be generated from an entry point. Do not execute any code other than declarations outside of the entry point for now.