Now also considers any attributes.po in the configured theme, if any.
Makes the attributes.extradictionary config setting obsolete.

We could use it everywhere, but it's better to reduce the already big
amount of configuration options the admin is confronted with than the
small problem this option solves.

* Conform SAML2INT; check AuthnRequest signature unless specifically disabled

* Migrate email utils to non-static

* Migrate http utils to non-static

* Migrate net utils to non-static

* Migrate random utils to non-static

* Migrate system utils to non-static

* Migrate time utils to non-static

* Migrate xml utils to non-static

* Upgrade notes

* Update test-framework

* Fix tests

* Migrate array utils to non-static

* Migrate attribute utils to non-static

* Migrate auth utils to non-static

* Migrate config utils to non-static

* Migrate crypto utils to non-static

* Raise coverage

* Fix rebase issue