Allow merchant to set the % discount for using XMR
Allow merchant to set the % discount for using XMR

This sets things back up so that the merchant can set the precise percentage that they want to use as a discount for paying with Monero like in commit f75790d90836e12a1c596c13f0a2a40c3d4a593e
monero-integrations/monerowp,monero-integrations/monerowp