Bug fix : when targets was copied, empty Directory (not contains any file) will be deleted.

If there are
c:\hoge
c:\hoge\fuga\piyo.exe
Old script will remove c:\hoge as there are no files right under c:\hoge.
Now I added file tree check to prevent these issue
Merge pull request #109 from guitarrapc/Bug_fix_for_Package.ps1

Bug fix : Package.ps1 have bug possibility of removing Empty Directory even it's child have file.