Moved assert to base class

git-svn-id: https://thermopower.svn.sourceforge.net/svnroot/thermopower/trunk@233 80daafeb-7430-0410-91d5-8b30b0bbd841
Fixed tests and examples

git-svn-id: https://thermopower.svn.sourceforge.net/svnroot/thermopower/trunk@234 80daafeb-7430-0410-91d5-8b30b0bbd841