RightClickDrag, Checkbox, PrefabLoad

-Added right click dragging on y axis. It's not perfect but it works for
now. It assumes each object is along the same Y plane (which isn't true)
-Added checkbox to decide the bounding box to use for random position
generation. The two options are preconfigured in the stimulus script
configuration
-Changed stimulus to be loaded from prefabs instead of already in-scene
objects. This helps performance and allows addition of arbitrary
stimulus with only minor memory footprint.

Still need to upload logger modifications and collision changes.