[#4226] Added test reproducing issue

- calling `allow($role)` after a resource exists should grant that role
  all privileges on all resources.
[#4226] Fix null resource/privilege assignment

- Prepend `null` to the list of resources when `null` is passed as the
  resource to `allow()`/`deny()`, ensuring that `allPrivileges` gets
  updated correctly.
Merge branch 'hotfix/4226' of https://github.com/weierophinney/zf2 into weierophinney-hotfix/4226
Merge branch 'weierophinney-hotfix/4226'