SAMLParser: Extract name and description from SP metadata.

This patch extracts the name and description of the SP from the
AttributeConsumingService element in the metadata.

Patch by gyufii (http://code.google.com/u/gyufii/), attached to
issue 252.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@2073 44740490-163a-0410-bde0-09ae8108e29a