Leave information on scanned Windows hosts

This routine stores information about the scan on the scanned host, provided it is a Windows system remote registry and wmi access. The information cover hostname, scan start time and scan end time. No details about the actual scan results are stored on the scanned host. By default, this routine is disabled even it is selected to run. To activate it, it needs to be explictely enabled with its corresponding preference switch. The preference 'Message' may contain 3 placeholder where respective content will be inserted into the message when the message is finally created on the target system: '::HOSTNAME::', '::SCAN_START::' and '::SCAN_STOP::'. At the end of the scan, the message will be written into the registry key 'SOFTWARE\VulScanInfo'.