Autocomplete page item cleanup - Woo Edition

[tw2113]

Branching this off from #435

Trying to do what we can to clean up some of the available content types that get listed on the Autocomplete settings page, for stuff that shouldn't need to be listed. This is largely "internal content".

1. Remove shop_order and shop_order_refund from the list.
2. product_visibility and product_shipping_class from term listing.

I doubt people want to be able to index orders and refunds on the frontend.

Item 2 can be modified in get_excluded_taxonomies(). These may be best off via using the available filter and only added if WooCommerce is enabled.