Added support for leaving out the samlp:NameIDPolicy in the request by setting...

Added support for leaving out the samlp:NameIDPolicy in the request by setting the NameIDFormat to null in the SAML 2.0 SP metadata. Requested by James Hartford.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@424 44740490-163a-0410-bde0-09ae8108e29a