Removing HTML tags from localized text

[dparker1005]

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Changes proposed in this Pull Request:

Alternative to #1994.

Updates "discount code applied" strings to all be the same and to have the <strong> tags outside of the localized string.

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[kimcoleman]

This works as is for codes applied during the checkout / on checkout page. When you pass a code via the URL I am getting numbers output at the end of the string. sprintf fixes, but I don't know if that's the right choice or there's another fix. Test with a url-applied code and see.

[dparker1005]

sprintf() is the correct choice, good catch!