Improved error handling in saml 2.0 initslo, as well as graceful fallback when...

Improved error handling in saml 2.0 initslo, as well as graceful fallback when cookie is lost for some reason

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@274 44740490-163a-0410-bde0-09ae8108e29a