Revert "#732 Optimized access to the TestClass by using a factory method and a shared pool"

This reverts commit 7092f460214aff75ea0daacb7ad6ab340396f93c.
#732 Revert partial: Modified JUnit core for reduction of code duplication within the experimental HierarchicalContextRunner.
#732 Implementation of the TestClassPool
#732 Moved Statements RunAfters and RunBefores