Add notebook runner utility for processStarTask and expose more Spectractor parameters

People need an equivalent to runDataRef to allow DESC folk to be able to easily process single visits from a notebook. Add a utility to make this easy for them.

Also, task should be fully configurable from our side, so expose most of the parameters as task config options.

This ticket is now a massive update to the new Spectractor, and has been open for way too long.