Bumping to Houdini Version: 13.0.504
Houdini Engine Version: 1.8 (API: 13)
On Mac, link against HAPI_Loader to avoid some library conflicts
Rename some variables
Put each output curve into its own transform

This makes it easier for viewport selection, and follows the usual Maya
convention.
Give each output curve node a proper name
Calculate knot sequences for curves with no knots