#55 WtkSmartLink task does not remove empty packages

[Stefano Turri]

Using WtkSmartLink task, I noticed that empty packages
folders are copied to the destination jar, increasing
its size slightly.

To avoid this effect the task class, WtkSmartLink.java
can be modified by adding the following line of code,
calling setFilesetonly on the destination jar object:

zip.setFilesonly(true);