Add support for {ITEM.STATE.ERROR} in Trigger-based notifications

We make heavy use of nodata Triggers. Most of the time they fail, because the item becomes unsupported. It would be very helpful, to include the error message, why the item failed, into the error message.

Example: With VMware monitoring, everything starts to fail, if the password expires. If that's the case, the item states that very clearly, while the nodata Trigger itself gives no obvious hint. Therefore, it would be helpful to get receive that information inside the action notification from the nodata trigger.