Refactored dashboard widgets into controller that can take another controller class for its content; listing widgets on the dashboard now handled by ListView controller
Removed object_widget.mustache for directives, which seems to be orphaned.
Merge remote-tracking branch 'origin/feature/generalized_dashboard_widgets' into feature/generalized_dashboard_widgets

Conflicts:
	src/ggrc/static/mustache/directives/object_widget.mustache