Add CycleTaskGroupObject.object to fix cache expiration

* Add migration, mixin, client-side attributes, and cache linkage for
  `CycleTaskGroupObject.object`
Update migration to fix existing CycleTaskGroupObjects
Add Cycle.is_current attribute

* Add migration and attribute; update filters/UI to use `is_current`
  instead of `status`.
get_state should only consider current cycles
b/15940077 Triggering hashchange event after tree item added, to show new TaskGroup expanded
Clear objects from memcache when updating a cycle
Enable more efficient query for expired objects in Cycle

* `get_cache_key` only requires `type` and `id`, so enable other
  representations of that data (tuple or dict)
* `Cycle.cycle_task_group_object_objects_for_cache` then only needs
  `object_type` and `object_id`, so no need to query for the full
  `.object` instance
Fix for more efficient query
fixed check-all button issue
Merge pull request #1565 from reciprocity/feature/multiselect-checkall-button-issue

fixed check-all button issue
Merge pull request #1558 from reciprocity/feature/fix-cycle-task-group-object-cache-expiration

Fix Cycle cache expiration and other issues
Set end date for cycle_task_group_objects when starting cycle
Whitespace fixes
b/16300640 Remove references to mockup classes
b/16324455 Move tasks to top of object nav list
Merge pull request #1568 from reciprocity/feature/workflow-remove-mockup-tree-references

b/16300640 Remove references to mockup classes
Merge pull request #1567 from reciprocity/feature/workflow-objects-end-date

b/16348276  Set end date for cycle_task_group_objects when starting cycle
Merge remote-tracking branch 'origin/develop' into feature/open-created-task-group
auto scroll fix for multiselect modal
Move TaskGroup auto-expansion code into Workflow controller

* Avoid unnecessary `hashchange` triggers
* Only trigger expansion behavior for TaskGroup