Add some fixtures that allow creation a fully formed instance.
Add some fixtures that allow creation a fully formed instance.

This shells out to create an instance, named test_instance,
removing one if it is already there.

TiddlySpace/tiddlyspace,FND/tiddlyspace,FND/tiddlyspace,TiddlySpace/tiddlyspace,TiddlySpace/tiddlyspace,FND/tiddlyspace