Allow OWServer binding to accept e.g. DS2423 dual counter, where counters are labelled Counter_A and Counter_B in the OWServer XML file.
Therefore, RegExp to check for valid item names has been extended to also accept underscore (_) in item name.

https://github.com/wuellueb/openhab/issues/1
Merge pull request #1409 from wuellueb/master

Allow OWServer binding to accept e.g. DS2423 dual counter, where counter...