CHEF-3404: Provider Resolver

Implements lazy evaluation of which chef provider to use based on evaluating the system.  Lets the the service resource select its provider based on interrogating the system rather than assigning a single default provider per distro.  Providers encapsulate their own logic for determining which resources they support.
It seems like this may be meant to be a singleton?  I haven't seen any use of Singletons in Chef Client code before - have I just missed them or do we generally not bother?