Iec 62056-21 meter binding

Sorry pull request came from wrong branch.
Now created pull request from right branch
 .
Re-forked newly from openhab master and added the binding.

Have been tested with some devices by me and other tester from forum.
The binding should work for any meter according IEC-62056-21.
I have used the openmuc library for the serial communication. it uses LGPL version 2.1 .
http://www.openmuc.org/index.php?id=49
Because of some differences in the usage of rxtx library i have reported a bug report to the project author.
I have ask him if i am able to reuse the code in htis binding. I left the original copy right header as is.

Wiki is ready. https://github.com/openhab/openhab/wiki/IEC-62056---21-Meter-Binding

Thx
Peter