Fix the decimal symbol in various places

This fixes how the numeric value in the tip input box is displayed, as well as a few places where the numbers are updated via JavaScript.
Yeah I noticed that; I just wasn't sure if I should tackle it in this PR. I think there is an easier solution. That string is already localized when sent from the server; this code is just updating it after you click the "Confirm" button. So, we should be able to make this only replace the number and not the surrounding text.