Removed deprecated methods from WC_Frontend_Scripts and rewrote script registration and localization to run once.

Closes #6338
[2.2] Use variation get_stock_quantity() for max_qty

Fixes #6339
[2.2] Prevent bulk edit cancel from clearing options.

Fixes #6344
remove notice for undefined action property of ajax request
[2.2] and test, use term_taxonomy_id for transient names
Merge pull request #6380 from haroldkyle/master

[2.2] Remove notice for undefined action property of ajax request
Minor tweaks to cart shortcode