Watir select list options should use watir elements

For Watir, the `PageObject::Elements::Options` returned by `SelectList#[]` and `SelectList#options` seem to be using the wrong underlying native element.

For example, for any page that has a select list, you can see that the underlying element of the select list is a Watir element (as expected):

````ruby
p page.select_list_element.class
#=> PageObject::Elements::SelectList
p page.select_list_element.element.class
#=> Watir::Select
````

When you get select list's options using `options`, you can see that the underlying is a Selenium object (unexpected).

````ruby
p page.select_list_element.options.first.class
#=> PageObject::Elements::Option
p page.select_list_element.options.first.element.class
#=> Selenium::WebDriver::Element
````

If instead you get an option using `[]`, you can see that the underlying object is a PageObject object, which has an underlying Selenium object (unexpected).

````ruby
p page.select_list_element[0].class
#=> PageObject::Elements::Option
p page.select_list_element[0].element.class
#=> PageObject::Elements::Option
p page.select_list_element[0].element.element.class
#=> Selenium::WebDriver::Element
````

Presumably, the underlying options should be using a Watir object.

I assume these methods were already under test, so I did not add any new tests.