Skip host discovery

[atarantini]

Add option for nmap: -Pn: Treat all hosts as online (skip host discovery)

Maybe run it as default and disabling it then using "--fast".

From Nmap Host Discovery documentation:

Host discovery is sometimes called ping scan, but it goes well beyond the simple ICMP echo request packets associated with the ubiquitous ping tool. Users can skip the ping step entirely with a list scan (-sL) or by disabling ping (-Pn), or engage the network with arbitrary combinations of multi-port TCP SYN/ACK, UDP, SCTP INIT and ICMP probes. The goal of these probes is to solicit responses
which demonstrate that an IP address is actually active (is being used by a host or network device)