[web, formatting] move Interval data type display logic from final view to printable_value (closes #1984742)
also, fix implementation so that negative time delta are properly considered
#! /bin/sh -ecase "$1" in remove) if [ -x "/etc/init.d/cubicweb-ctl" ]; then invoke-rc.d cubicweb-ctl stop || true fi ;;esac#DEBHELPER#exit 0