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.

"""Multiple delete."""
        if any(item.pool == models.Pool.DEFAULT_POOL_NAME for item in items):
            flash(f"{models.Pool.DEFAULT_POOL_NAME} cannot be deleted", "error")
            self.update_redirect()
            return redirect(self.get_redirect())
        self.datamodel.delete_all(items)
        self.update_redirect()
        return redirect(self.get_redirect())
    @expose("/delete/<pk>", methods=["GET", "POST"])
    @has_access
    def delete(self, pk):
        """Single delete."""
        if models.Pool.is_default_pool(pk):
            flash(f"{models.Pool.DEFAULT_POOL_NAME} cannot be deleted", "error")
            self.update_redirect()
            return redirect(self.get_redirect())
        return super().delete(pk)
    def pool_link(self):