Added Insteon PLM binding. Fixed urtsi binding.

Added a binding that communicates with an Insteon Network via a PLM modem.

This pull request also fixes a problem in the urtsi binding: adding 
System.setProperty("gnu.io.rxtx.SerialPorts", port);
to UrtsiBinding.updated()
allows the serial port to be found even if the device is sym-linked like:
/dev/urtsi -> /dev/ttyUSB0