Garbage collection

Added a mark and sweep garbage collector to my language, it walks the roots, marks every used object, then frees all unused objects!

Most impressive part of this(in my opinion) is that most of the garbage collector is actually written in my language

Misc

• The garbage collector gets called automatically every 1 second, but you can turn it off (CompilationConstants.AUTOMATIC_GC)
• If you want to manage memory manually, you can turn off the garbage collector entirely (CompilationConstants.MANUAL_MEMORY)