Add show history button to Workflow Tasks

Story: https://reciprocitylabs.atlassian.net/browse/CORE-6
b/17062748
I really don't like this here, but it's similar to how filters work on admin dashboard (list_view_controller.js).

I wanted to add this event to `content_controller_options`, but it just got a bit messy (binding custom events to this.element once the control was rendered).

The other option was extending TreeView, but that didn't feel right either.

Does canjs have a clean way of extending Control events per instance?