Add IGNORE_ERRORS to FileUtils.delete()

Add IGNORE_ERRORS to FileUtils.delete()

There are a few situations where you want to delete files or folders but
where you are not interested in getting exceptions if this doesn't
succeed. E.g. if you delete garbage in the GC class you want that if
certain files can't be deleted the command succeeds. Maybe the next
garbage collector run has more luck not to interfere with a virus
scanner run on Windows. Therefore an option is added to
FileUtils.delete() not to report errors in such cases.

Change-Id: I58994d8c481e591dcbb0f2be7dfa562e125f0f08
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>