Cleaned up a bit of the Julia renderer

[B-rando1]

I split up a few functions, added some comments, etc.

Notes:

• I noticed that the getUsing function and things relating to it are only used by the C++ renderer, so I removed them from the Julia renderer.
• I removed the TODO: think about splitting up CodeType comment. I'm not sure if that is the way we should go, and if it is then it should be an issue, not a comment.
• I removed the block comment describing Julia's abstract types. I do still think that adding sub-types to GOOL would be a neat project, but there's no reason for that comment to be there.
• I created the jlGlobalDec function that jlAssign, jlSubAssign, and jlIncrement all use.
• I removed spaces at the end of lines and evened out the spacing in one or two places.