Deploy phpBB datastores

Summary:
Create datastores directories and provision them
with the mutable directories from phpBB repository.

Are considered as mutable directories:

• config/
• ext/
• files/
• images/
• store/

Ref T1377.

Test Plan: salt equatower state.apply roles/paas-docker/containers/phpbb

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1377

Differential Revision: https://devcentral.nasqueron.org/D1520