Fix case on User model name in a1 config
Adding ACL tests and fixing issues during testing

* Add api.acl.feature
* Improve Ushahidi_Api::_check_access() to allow easier overriding of the
  resource being checked. This is so we can pass a Post object to
  acl assertions.
* Extend _check_access() in Posts to grab the requested post and check
  its access
* Override Acl_Assert_Argument to fix errors if resource fields are not
  defined.
* Update Acl_Assert_ArgumentStatic to fix similar errors
* Update a2 config to fix GuestCanCreatePost rule and reformat
* Update posts tests to keep them working
Filter /posts collection based on user allowed access

* Only include posts if access check passes
* Add extra draft posts for testing
* Add tests for admin and user seeing private posts in collection
Add status filter to /posts and filter by published by default

* Rename test attribute status to missing_status to avoid conflict
* Add status=all filter to acl tests
* Add status filter code in posts controller