Add an offline flag for a host and subnet

[opennetadmin]

In the host dialog and creation/modify add an offline flag. This will default to false/no but can be set to true.

The intent here would be to allow a host to be flagged as offline so that things like DNS/DHCP builds do not process anything related to the host. Also ona_nmap_audit scans or any other process within the system can ignore the host as needed.

It should also have a timestamp of when it was flagged.. so maybe its just a date field that if it is populated its flagged, if its blank then its active.

Do the same for subnets