Add old shift instructions
Add push/pop
Fix minor overloading bug
Replace str_starts_with() with str.startswith()
Add back old set class with Mutagen-only implementation
Improve slice() builtin
Add set.__sub__
Add set.pop()
Add dict.keys(), dict.values()
Allow parser to handle 'from module import x, y, z' syntax
Print list/dict comprehensions properly
Some minor asm.mg cleanups