Bug 1005100 - Create one time tasks

This addresses the mixins and methods required to prevent access to non-repeatable tasks to
which a user should not have access

A subsequent PR will be issued to address changes to the view logic for the buttons
Merge pull request #137 from bobsilverberg/one-time-tasks

Bug 1005100 - Create one time tasks
Bug 1005127 - [privacy] Add ability to delete profile