SAMLBuilder: Move ArtifactResolutionService to the correct position.

According to the schema, the ArtifactResolutionService element(s)
should be located before the SingleLogoutService element(s).

Patch by Danny Bollaert <danny.bollaert@gmail.com>.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@2184 44740490-163a-0410-bde0-09ae8108e29a