modified the configuration class so it allows multiple simultanous instances. This is important in the case where you write a separate application that makes use of simplesamlphp and also make use of the simplesamlphp libraries as the template system where the template directory is not the same as for simplesamlphp itself. I am writing an application called openwiki where this is important. should not break existing code, and no modifications neccessary in other simplesamlphp files.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@239 44740490-163a-0410-bde0-09ae8108e29a