Moving the creation of the 'CubeTools' distribution to it's own task.

The standard Gradle lifecycle tasks will not longer create the CubeTools
distribution along with the GIPPtools distribution. In the future the
new task 'assembleCubeTools' must be used for the CubeTools.

The usual 'build' and 'assemble' tasks will continue to build the
GIPPtools distribution (only).