(maint) updating metadata.json
(maint) remove unnecessary code

This removes commented out and deemed unnecessary code
(maint) updating documentation on owner
switch to String.empty?

This switches validation checks to use Ruby's String.empty? check which
works on 1.8.7 as well
(maint) add comment on default for :owner

 :owner should default to platform specific setting, where right now the
setting is based only on Windows, which will be incorrect once we support
other platforms.
Do not allow :permissions => []

This will require a change to the armature. After discussing this more at
length, someone may have a bug in their hiera and it could potentially cause
a world of hurt if all managed  acls were purged of users.