Introduction of a button to manually initiate an attack in the MitM scenario

[manosf]

This branch is a child of manosf:sniffer and thus this PR contains changes made in #1560 which is not yet merged to master.

This PR serves two mutually inclusive purposes:

1. Introduce a TUI button that the user can press to trigger a phishing attack during the MITM scenario. (i.e. when --mitminterface/-mI is used).
2. Refactor the triggerring of the sniffer module from Packet sniffer module #1560 to use Asynchronous Sniffing[1] instead of Python's Threading in order for the module to be able to get shut down and free resources, while avoiding any file corruption risks.

[1]: Introduced in Scapy v2.4.3 with secdev/scapy#1999, hence the new version requirement in setup.py.

How it works in short

As soon as the user chooses to press the button, the sniffing module is stopped gracefully, the firewall rules are cleared and then are reset to redirect all traffic to localhost and WifiPhisher's tornado webserver commences operations for handling localhost traffic and rendering the chosen phishing template.

Unexpected behaviour

If a non-forcing option is used (e.g. -nD/--nodeauth), once the user presses the button, the connected victim simply ceases to have internet access as expected, however they do not get prompted with the phishing template. They need to reconnect to the same or a different rogue AP in order for the template to be displayed to them.