Add a '--ab-decision' flag

[thesp0nge]

Add a '--ab-decision' flag. Can be a good idea to make dawnscanner able just to say a quick "go/no go" for a release with a small json output like {decision:"GO", vulns: 12, mean_cvss: 3.2} or {decision:"NO GO", vulns: 9, mean_cvss:9.2}