Add Spoofable flag and graph

[dotBATmanNO]

[Feature request proposed by colleague]

Add check to claim that a domain is Spoofable

• This test should be on by default, but also be disabled with the flag -CheckSpoofable 0

• Output should have a flag for IsSpoofable.

• Another graph should be created.

Flag should be True if any of the following conditions are met:

• Lack of an SPF or DMARC record
• SPF record never specifies ~all, -all
• DMARC policy is set to p=none or is nonexistent