Onewire plugin - support full owfs path, add more device families

Hi,

this is cleaned up extension of the onewire plugin as sent earlier (http://mailman.verplant.org/pipermail/collectd/2011-November/004810.html). Basically adds two new families (new types of thermometers) and also an option to directly specify full OWFS path to the device parameter to be read (see updated man page and my earlier post). It is fully backwards compatible.

Regards,
Tomas