Convert and move GraphSampleData class into a grouper/misc gsh script

The GraphSampleData class was created as a quick way to test sample data when visualization first went live. Going forward, it isn't necessary to have this as a Java class that needs to be compiled along with other classes, and doesn't need to be included with everyone's installation.

There is already a grouper/misc/visualization folder, which contains general proof of concept gsh scripts. This would be a suitable place to hold the gsh version of this class.