(SERVER-112) clean up master.rb

In some forthcoming changes for SERVER-112, I'm going to need to pass some additional data in to the constructor of the `Puppet::Server::Master` class.  As I was refactoring it to allow this, I felt like a general cleanup was overdue.

This PR has several incremental commits that lead to what I think is an improved organizational structure for the relevant code that used to be in `master.rb`, and which will make it much easier/cleaner for me to do the follow-on work for SERVER-112.


Should we move this up to the top of the function so that any log message that might be written out during one of the earlier calls would be possible to capture through logback?