Improve module documentation and commenting

[pipitone]

This is an unhelpfully imprecise ticket title as is, but let me explain here and we can perhaps break out separate tickets if that seems more useful. I think we are missing some important bits of documentation for the new (or returning after ~2 years) user:

• Module documentation to describe in more detail how to use qbatch from the command line and programmatically (a good start in the README already)
• Additionally, commenting to describe how we've organized the code. The use of globals, for instance, is a little strange, so it's probably worth orienting the reader to that.
• Function documentation, especially of argument structure, side effects, and return values. This is not always obvious, e.g. qbatchDriver()
• Certain sections of the code are a little opaque on first read and could use some commenting. For instance, what does standard_library.install_aliases() do?