regexps fixed for collectd 5.x

Collectd 5.x graphite_writer plugin produces metrics like:
collectd.host-1.memory.memory-buffered
collectd.host-1.df-root.df_complex-reserved
collectd.host-1.disk-dm-0.disk_octets.write
Original regexps doesn't match such metrics.
Conn (http://metrics20.org/spec/)