Dynamic Detection of SPNEGO auth method and adding of NegotiationAuthenticator

Previously a mapping for the SPNEGO auth method and the authenticator had to be manually defined, this capability is not present in AS7 however it is suggested that alternatively we can detect the auth method ourselves and dynamically add the valve - this seems cleaner as it potentially allows SPNEGO to be added/removed from a server without manual configuration being required.

It is suggested to look at the following code for an example where a valve has been added dynamically before: -
org.jboss.as.jpa.processor.PersistenceUnitDeploymentProcessor in the JPA subsystem.