* Improve the way we do queries
* PHP legacy compatible
* Update aproach to filter queries with empty values
* Fixing Unit Tests
* Moving Unit Test to its the correct test function
* Filter missing the new param, allow_empty, also simplifiying unit test.
* Helper function to create counpon does not support empty coupon codes
* Helper function does not need to allot empty search
* Wrong code standard
* Fixing Code Standard Unit Test
* Fixed case for all _e, esc_attr_e and esc_html_e strings
* Fixed case for all _n_noop strings
* Fixed case for all _x strings
* Fixed case for all __, esc_html__ and esc_attr__ strings
* Fixed a few more strings
* Fixed strings in unit tests
* Fix PayPal Standard case.
* Save Order text
* Added missing param tags to functions
* Added comments to `wc_get_attachment_image_attributes` and
`wc_prepare_attachment_for_js`
* Fixed return type value for functions where it says bool but the code
returns array
* Renamed boolean to bool
Changes:
- WC_Cart::coupons_enabled() to wc_is_coupons_enabled()
- WC_Cart::get_cart_url() to wc_get_cart_url()
- WC_Cart::get_checkout_url() to wc_get_checkout_url()
This methods can be used in any place, but WC_Cart() is present only on
the frontend.