add customer details and addresses to emails via `woocommerce_email_customer_details` hook
make `woocommerce_email_order_meta_keys` filter args match `woocommerce_email_customer_details_keys`
fix variable naming error
add filter to rename Customer Details section
change array to account for localization per @claudiosmweb
Merge branch 'email_customer_details_hook_backup' into email_customer_details_hook_2

Conflicts:
	includes/class-wc-emails.php
Merge pull request #6735 from helgatheviking/email_customer_details_hook_2

Email customer details hook
Fixed the labels in customer details
Improved the WC_Emails::order_meta() method

Deprecated the woocommerce_email_order_meta_keys filter in favor to woocommerce_email_order_meta_fields

Now we can filter and work with the data without worrying about translations.

cc: @mikejolley @helgatheviking
fixed the deprecated filters
layered nav count markup matches product/post categories. #5606
remove border-radius vendor prefix. #5606
remove opacity vendor prefix. #5606
remove box-shadow vendor prefix. #5606
refine gradient mixin. #5606
remove transition vendor prefixes. #5606
remove scale vendor prefix. #5606
remove box-sizing vendor prefix. #5606
activation.scss and admin.scss coding standards. #5606
dashboard.scss coding standards. #5606