Make permissions more granular

wf_job should offer per environment permissions for actions. This will ensure greater control over what actions people can perform on a particular job. The current permissions model is built for the original concept of multiple instances of a single site.

The implementation should be similar to Drupal core's per node type permissions where the node types, or in this case the environments, are iterated over the create more granular permissions. There should be a generic permission callback which takes 2 arguments - the action and the job (to fetch the current environment for the job). This should be callable by the permission callback in the hook_menu implementation.

This was implemented in r83ff55b.