Add translation English to Korean

Update translation
Add transition English to Korean

Update Language
Add trainsition English to Korean

Update transition
Add admin transition file of English to Korean

Add admin transition file of English to Korean
Korean transition update.

Changing the WooCommerce to the korean makes error on report graph so, I
put it back as it is
Update Korean Transition

Update Korean Transition
Update Korean Transition

Update Korean Transition
Update for korean Transition

Update for korean Transition
Spanish translation update

Spanish translation extended and improved.
Duplicate capability hook
SKU: search case insensitive support

As committed in master as well: https://github.com/woothemes/woocommerce/commit/a93cee0cbac395800e9276c596a6329f9968d6c9
Cast term_id as int before using in has_term

As committed in master branch: https://github.com/woothemes/woocommerce/commit/7a21dacf5ba7b6a34468014b0e04b13a34f572c5
Added previous two changes to changelog
RUB currency symbol fixes

As done on master branch:
- https://github.com/woothemes/woocommerce/commit/683d54f957cf4437a213fa8483b580ddae9a5596
- https://github.com/woothemes/woocommerce/commit/1671b1d713f0af4f6a779e85deec005aebd8e98f
esc_js for translatable string in the javascripts

As on master branch:
- https://github.com/woothemes/woocommerce/commit/ba923875a20b66292d4b5c2a4f492506cb4a4a99
- https://github.com/woothemes/woocommerce/commit/3f1bca59ccf006480447d24cec7bbdb4cd7619a1
More esc_js action to prevent errors with translations

As committed on master branch:
- https://github.com/woothemes/woocommerce/commit/38d892b14e26df435e90b2f13f48693d28bc23d4
Update ro_RO frontend translations
Updated the correct doc block for return type
PayPal button should use 'button' and 'alt' classes. Closes #3096
PayPal button should use 'button' and 'alt' classes.

As committed on master:
- https://github.com/woothemes/woocommerce/commit/00cbde04e5585aa36a3622709d38a87a66ce8757