Changes to ordinal functions

The ordinal functions are first, second, third, ..., last, etc.

There are two changes of interest:

	Change1	Ordinals are now of type `native!` not `action!`
	Reason	Polymorphic application of these functions across all series datatypes improves the implementation.

And:

	Change2	Ordinals no longer throw an error on a past-end condition.
	Reason	Behavior is now similar to `pick`, returning none when past end. Experience has shown that making the ordinals throw errors when past-end was not convenient for the most common coding practices.