Ensure TaskGroup is refreshed when TaskGroupTask is created
Remove uniqueness constraints on Workflow and TaskGroup

* Titles need not be unique anymore
Move 'Activate Workflow' to be a can.Component
Enable "Clone Workflow" functionality

* Adds `copy_into` method on Identifiable mixin
* Adds `copy` methods on Workflow, TaskGroup, TaskGroupObject,
  TaskGroupTask
* Adds `workflow-clone` can.Component
* Adds handling for `clone` attribute on Workflow during Workflow POST
Merge remote-tracking branch 'origin/feature/workflow-simplification' into feature/workflow-simplification
Extend and fix relative date functionality
Add configurable start date to Active Workflow dialog
Add actual relative dates in TaskGroupTask display