Adding a session->getsize class to measure the size of the session. I also...

Adding a session->getsize class to measure the size of the session. I also removed the reference to the configuration class which saved 12% size of the session size... will be further reduced... hold on.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@202 44740490-163a-0410-bde0-09ae8108e29a