Lcg/script resource fixes

Execute and Script Resource improvements

- Warning on incorrect usage of the command resource in any script
  resource
- Warning on code in script resource being nil
- Specs added to force deprecation of incorrect usage in Chef-13
- Specs added around the (supported) incorrect usage in Chef-12
- Cleanup+Modernization of providers and specs
- Fixed some global state bugs around the Chef::Log.level in the spec
  tests
Hmmm....  Yeah, but i can just create a visual block and ',a:' to fix it all via vim's tabularize...  I can see the argument that the person who is not a software dev and doesn't spend any time trying to learn how to quickly fix indentation issues like this shouldn't have the barrier to entry for submitting PRs on the codebase.  At the same time I think we should also be better at taking PRs and making a quick pass over them to fix issues rather than sending back to the requestor for super nitpicks like whitespace.