Permissions system

[wonderchook]

Permissions system: the reusable backend component of this is https://github.com/Cadasta/django-tutelary.

Initial use in platform: back-end system for policy-based access control (data model, policy grammar, permissions engine); fixed roles defined by developers; no user-visible reference to policies, user-level permissions, etc.

[ian-ross]

Remaining tasks here based on code review with @oliverroick:

• Support function views
• Documentation improvements
• End-to-end tests
• Better treatment of collective actions
• Policy update handling
• Modify policy format to allow for comments
• Caching for performance
• Django admin interface (low priority: not directly needed for Cadasta)

[ian-ross]

I'm closing this now, as the individual tasks are all there as tickets on the django-tutelary repo.