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
isn't max size of the PATH env variable 2k?  ie. http://brucebcampbell.wordpress.com/2014/04/13/path-environment-variable-max-size-limit-and-related-ills-on-windows-7/

i haven't been able to dig up real windows documentation on this since most google results are for the 256-ish MAX_PATH issue...