Noting a message security change

[Cantor, Scott]

I just worked out a middle ground solution to an old request from Kaspar 
to turn on message signing by default so that people who want to start 
pushing message security over TLS don't have to get people to change 
defaults.

https://issues.shibboleth.net/jira/browse/IDP-76

It's a bit weird at first glance, but I think it's a good compromise.

I'm proposing (and checked in) a change to the meaning of the 
"conditional" signing/encryption flags so that by default they turn on for 
port 443 (or in the absence of TLS) and turn off otherwise. The difference 
being that they're on for port 443, which is the most likely SOAP port 
used by somebody that's trying to avoid using the transport layer 
certificate for SAML trust.

Anybody using 8443 or anything but 443 with TLS for SOAP sees no change 
(conditional means no signing/encryption), so the impact is confined to 
the audience Kaspar is trying to reach.

In the "worst" case, somebody using 443 already might suddenly get 
signing/encryption turning on, which doesn't seem very likely but also not 
very harmful, since the request here was actually to do it by force.

I also included a property that restores the original behavior.

Does this provoke any violent objection?

-- Scott