Added a polyline, and basic support for rendering it

I think we can pull the strip generation code into a helper too, but
copied/pasted for now to see it working.

Change-Id: If7f600d57b8a9d495330ec229abaf2c852edd593
Refactor uniforms a little, enable point rendering again

Change-Id: I5fef417f159815e96dab719926f8e303f9b748b9