COMP: Trying to fix java parallel build hiccups in modular.
This is a follow-up to pre-modular commit 875f8232, which was a temporary fix to the java parallel build failure. When the build fails, errors of the form "class file contains wrong class" are seen. This patch reorganizes and comments the cmake code for clarity. It will probably not fix the problem, but it should at least assist in determining the cause. This commit also puts vtkBuildAllDriver.class back in java/vtk, the modularization commit 0c1471f1 moved it from the java/vtk dir to the java dir. Change-Id: Icee402497f2d64a4dd6314a2f31e05c4e0805b91