Add a basic OSL shader that shows how inputs and outputs work and do some simple math with them. This template is a happy medium between the templates we already ship, empty_shader is a little too bare, and the other templates are a little "too much" and you end up having to delete a whole bunch of stuff. a great starting point for some experimentation! Differential Revision: https://developer.blender.org/D9933 reviewed by: brecht