New DGNs, INVERTER_CONFIGURATION_STATUS/COMMAND_4, and updates to INVERTER_CONFIGURATION_STATUS/COMMAND_3

Submitted by Xantrex, two new DGNs

INVERTER_CONFIGURATION_STATUS_4 (1FE9Bh)
INVERTER_CONFIGURATION_COMMAND_4 (1FE9Ah)

and additions to INVERTER_CONFIGURATION_STATUS_3. INVERTER_CONFIGURATION_COMMAND_3 .

These support additional features not already in the RV-C specification.