The DAGs main page has All/Active/Paused.

It would be nice if we can have also Running Now which will show all the DAGs that have at least 1 in Running of DAG runs:
![Screen Shot 2021-08-25 at 11 30 55](https://user-images.githubusercontent.com/62940116/130756490-647dc664-7528-4eb7-b4d8-515577f7e6bb.png)


For the above example the new DAGs tab of Running Now should show only 2 rows.
The use case is to see easily what DAGs are currently in progress.

elif isinstance(form_fields[k]["value"], dict):
                    form_fields[k]["schema"]["type"] = ["object", "null"]
            
            if (
                "description_html" in form_fields[k]["schema"]
                and form_fields[k]["schema"]["description_html"]
            ):
                form_fields[k]["description"] = Markup(form_fields[k]["schema"]["description_html"])
            if "custom_html_form" in form_fields[k]["schema"]:
                form_fields[k]["schema"]["custom_html_form"] = Markup(
                    form_fields[k]["schema"]["custom_html_form"]
                )
        if not dag_orm:
            flash(f"Cannot find dag {dag_id}")
            return redirect(origin)
        if dag_orm.has_import_errors:
            flash(f"Cannot create dagruns because the dag {dag_id} has import errors", "error")
            return redirect(origin)
        recent_runs = (
            session.query(
                DagRun.conf, func.max(DagRun.run_id).label("run_id"), func.max(DagRun.execution_date)
            )
            .filter(
                DagRun.dag_id == dag_id,
                DagRun.run_type == DagRunType.MANUAL,
                DagRun.conf.isnot(None),
            )
            .group_by(DagRun.conf)
            .order_by(func.max(DagRun.execution_date).desc())
            .limit(5)