Re-add all filters of widget on change of category

At the moment all filters that were applied via the layered nav filter
widget are gone on changing the category with the product category
filter
Class instead of id for product categories widget

Also rewrote plain old JS to jQuery
Bugfix: swapped lines select and option
Renamed function get_order to wc_get_order
Changed use of get_order with wc_get_order
Merge pull request #6037 from barrykooij/refactor/wc_get_order

Refactor/wc get order
Merge pull request #6023 from krautnerds/master

Re-add all filters of widget on change of category
Revert "Merge pull request #6023 from krautnerds/master"

This reverts commit 9deee73b725aebcdccca0e6fdcb738a9cc4256c1, reversing
changes made to 1965c2b78684e2889a93cb0b9f9bfde5d01e7aa3.
Passed $args to dynamic class that inherits WC_Abstract_Order is never used.
Therefor the $args in the function and method in factory class seems unnecessary.
fixed simplify ssl notification url
Variation level backorder 'parent' option makes no sense now parent backorder select is hidden

#6035
Availability with backorders not requiring notification.
improved the simplify scripts
changed the simplify keys order
created API for get order refunds
created method API to get individual order refunds
added API method for create an order refund
Tweak language used for i18n_product_type_alert
created initial API method for edit order refunds
created API method for delete order refunds