Merge pull request #1800 from opscode/sersut/chef#1634

DSCL User Provider Rewrite
Conflicts:
	.gitignore
	RELEASE_NOTES.md
	chef.gemspec
	lib/chef/provider/user/dscl.rb
Merge pull request #1816 from opscode/sersut/port-chef-1800

Merge pull request #1800 from opscode/sersut/chef#1634