Use p2p ValidationResult (Ignore) instead of just Accept/Reject

[danwt]

TX/Block validator on new fork
    	// ValidationAccept is a validation decision that indicates a valid message that should be accepted and
    	// delivered to the application and forwarded to the network.
    	ValidationAccept = ValidationResult(0)
    	// ValidationReject is a validation decision that indicates an invalid message that should not be
    	// delivered to the application or forwarded to the application. Furthermore the peer that forwarded
    	// the message should be penalized by peer scoring routers.
    	ValidationReject = ValidationResult(1)
    	// ValidationIgnore is a validation decision that indicates a message that should be ignored: it will
    	// be neither delivered to the application nor forwarded to the network. However, in contrast to
    	// ValidationReject, the peer that forwarded the message must not be penalized by peer scoring routers.
    	ValidationIgnore = ValidationResult(2)
    	// internal
    	validationThrottled = ValidationResult(-1)

        Recommendation: make validator return ValidationResult