Merge branch 'default-operation' into single-logout

Conflicts:
	lib/passport-saml/strategy.js
validation part of xml contents extracted to parameter
SAML accepting LogoutRequest, not responding correctly yet
strategy prepared to have logout response functionality
generating LogoutResponse
fix 'self not defined'
Fix 'this._saml' to 'self._saml' in deeper context
Fix dangling `pass` call