function ones4d( shape ) {
	return filled4d( 1.0, shape );
}
Returns a four-dimensional nested array filled with ones.

@param {NonNegativeIntegerArray} shape - array shape
@returns {Array} filled array

@example
var out = ones4d( [ 1, 1, 1, 3 ] );
// returns [ [ [ [ 1.0, 1.0, 1.0 ] ] ] ]