Raise polyline to surface

#1706 

`PolylineGeometry` and `SimplePolylineGeometry` are raised to the surface of the ellipsoid by default.  To get a straight line, set `options.raiseToSurface=false`.

Also cleaned up functions in `PolylinePipeline` and tweaked sandcastle examples.
This is intentional.  The generateCartesianArc function doesn't include p2.  There's a comment about it above the function.