Add Teracom Ethernet I/O controller support

Attached is a patch to add support for Teracom Ethernet I/O controllers. We're using these controllers for remote management of our pop-locations (monitoring temperature/humidity and controlling fans/heating/lock).

To be able to differentiate between sensor types connected to the analog inputs the first two characters of the input description are evaluated: 'I ' = current, 'F ' = frequency, 'H ' = humidity, default type = voltage.

Tested with TCW240B http://www.teracom.cc/products/tcw240b-data-acquisition-module/