Jdmundrawala/windows env path

Fixes issues: 
https://github.com/opscode/chef/issues/2016 
https://github.com/opscode/chef/issues/2009

Includes changes from/Should replace:
https://github.com/opscode/chef/pull/1876
This uses the windows api instead of find/replace and I've added functional tests
Also this should probably go in a re-usable mixin or Chef::Util::Windows object.  I expect this isn't the last time we'll have to expand %-things on windows.