Add support for AI excitation properties

http://zone.ni.com/reference/en-XX/help/370471AA-01/mxcprop/func17f4/

http://zone.ni.com/reference/en-XX/help/370471AA-01/mxcprop/func17f5/

http://zone.ni.com/reference/en-XX/help/370471AA-01/mxcprop/func17fb/

http://zone.ni.com/reference/en-XX/help/370471AA-01/mxcprop/func17f6/