First cut at Clockwork configuration.  #3127.

This doesn't yet work because NcsNavigator::Core::RedisConfiguration
contains code that can only be evaluated with the Rails application
environment, but I thought it should be committed anyway so that others
can see what scheduled jobs ought to be like.

Separting RedisConfiguration from Rails will be tricky, but I think it's
doable.  The major points that need to be addressed is removing
ActiveRecord::Base and Rails.logger references from the code.