Updated FAQ with sample data link

FYI to troubleshooters: Related to this post I updated the FAQ for the Nightly and 4.10 wiki pages to include a link to sample dicom data that people can use to test their slicer installation.

https://www.slicer.org/w/index.php?title=Documentation%2FNightly%2FFAQ%2FDICOM&type=revision&diff=60442&oldid=59503