Refactor Axe helper show_ functions to should_show_

[adampatterson]

Create a helper file for the boolean functions.

1. show_template
2. show_woo_listing
3. show_woo_category
4. show_woo_single_product
5. is_sub_page

https://github.com/adampatterson/Axe/blob/e404e48ba49ca8422cbe997d637d508cae046c0d/templates/partials/admin-helper.php#L46

Used in the base theme entry points like page, single, and index.