Lots of cleanup and refactor

Created by: stratact

• Remove an unneeded clone
• Cleanup the way #[derive] is used on a few types
• Derive Default for parser::Job and use Job::default() instead of Job::new() which did the same thing
• Use BTreeMap for shell variables to have it automatically be sorted for reading
• Remove an unneeded binding in on_command()
• Use a type alias for BTreeMap<String, String> everywhere for easier maintenance