Remove unused, outdated and non-working SessionTests

The SessionTests seem to have been disabled for decades. They no start
at all because they do not find their data directories and even if they
are fixed to find them, most of those tests fail. In addition, they
introduce dependencies to the SessionTestSuite that is about to be
removed.

This change removes the unused SessionTests, their data, launch
configuration, and reference in the tests.xml, which has been
deactivated for decades. Some classes used in other tests are moved to
the according packages.

Author: HeikoKlare