Enable multiple current cycles

* Add per-cycle "End Cycle" buttons
* Add "Due" date to Cycle tree tier 1
Merge remote-tracking branch 'origin/develop' into feature/multiple-current-cycles

Conflicts:
	src/ggrc_workflows/assets/javascripts/controllers/workflow_page.js
	src/ggrc_workflows/assets/javascripts/models/cycle_models.js
	src/ggrc_workflows/assets/mustache/cycle_task_groups/current_cycle_header.mustache
Merge pull request #1586 from reciprocity/feature/multiple-current-cycles

Enable multiple current cycles