Support csv-import of currency prices (solution provided)

Hi

When importing products to WooCommerce using a .csv, the currency-price-fields are not updated, but new ones with lower-case currency codes are created in the database.

An example is: _alg_currency_switcher_per_product_regular_price_DKK

It is exported correctly when exporting from WooCommerce, but when importing, it creates this instead, which is then not used:
_alg_currency_switcher_per_product_regular_price_dkk

I fixed it by adding strtolower() around the $currency_code three places. I’m not a pro programmer, so I will not explain exactly where, but you can use this as a guide for your own solution. I would recommend somehow fix the plugin to support import/export in the future, for example by not using uppercases in field names.