Clerks cannot delete boards

Based on feedback from check-in
(see https://pm.theworkdept.com/issues/3484), prohibit clerks
from deleting boards.

Addresses #3484
Allow clerks to publish and unpublish content in their city

During the check-in meeting, the requirement surfaced to be able to
unpublish content rather than deleting it.  See
https://pm.theworkdept.com/issues/3520.

This is implemented using the permissions added by
https://drupal.org/project/publishcontent

Addresses #3484
Merge pull request #9 from ghing/3484-clerks_unpublish_not_delete

Allow clerks to unpublish content