Audit code before end of 2018

[Cliabhach]

This codebase has changed a lot since the first commit. @sam33rdhakal and myself will undertake a basic audit, looking for the following things:

• Code we don't understand
• Duplicated code
• Unused code
• Over-complicated code

We'll create PRs for these as we see them, and link them back to this issue. Note that we are not looking to make any significant changes to business logic; if they do get proposed, such changes will be highlighted.

You can follow along with our progress in the branch code_audit; I'm adding comments and questions in the branch pc-identify-codebase-problems-2018.