#89 TestHarness deletes scratch directory without warning

[Joel Dice]

In the 9.12 Bach release, the TestHarness.makeCleanScratch method deletes the scratch directory and anything it contains without warning. This might be reasonable if the user has explicitly specified the directory to use, but if the default is used, the user will lose whatever data happens to be in a directory named "scratch" under the current working directory. Just because such a directory exists does not mean it was created by a previous DaCapo run or that it's okay to delete it without at least warning the user and giving him or her a chance to specify a different directory.