Split config related fns out of services.clj and into it's own namespace

I need to add a new config option for [debugging catalog hash misses](https://projects.puppetlabs.com/issues/22977) along with some validation and code to create the directory when it's not there.  It seemed like a good time to break the config stuff out from the services.clj.  There shouldn't be any functionality change, as it was just a move of the code.  There was one side-affecty part of the existing code, which was to def the config.  It doesn't look to be used anywhere, so I removed it.

Eventually I would like to get that sort of global information, along with the jetty server, job execution pools etc in a top level atom.  The config.clj stuff could still be stateless, but the result of invoking config would be state in services.clj.  This commit doesn't do that stuff, but is a step in that direction and a pretty small change.