Run regression tests for the assembler

[krasin]

I have a collection of tests for DCPU16 assemblers (it's not that large now, but this would be improved over time) here: https://github.com/krasin/dcpu16-tests/tree/master/asm

It makes senses to run these regression tests with your assemblers to make sure that it has no known issues and (which is more important) to make sure that all the bugs you will fix in the future, will not appear later.

This issue is to write a script that will run deNULL assembler on these tests.