NETSHRVAR: improve alarm handling

Currrently NETSHARVAR does not alarm when the data is bad, or propagate and "in alarm" data quality attribute from the shared variable.

If data quality shows CNVDataQualityInAlarm then alarm the PV, this probably indicates a min/max limit but not sure how to tell which. May only be able to set MINOR severity and then choose a generic status like SOFT? There is HWLIMIT but it doesn't feel quite right.

If data is not "good", then raise an INVALID severity with appropriate status