Configuring available currencies in the CONFIG is not reversible

[krbz999]

Running a script such as

Hooks.once("setup", function(){
  const data = {
    hg: {label: "Heartnergold", abbreviation: "hg", conversion: 0.25},
    ps: {label: "Pansun", abbreviation: "ps", conversion: 2},
    cd: {label: "Credits", abbreviation: "cd", conversion: 200}
  };
  foundry.utils.mergeObject(CONFIG.DND5E.currencies, data);
});

does not immediately display any added currencies on the character sheet. Secondly, if one was to later remove currencies, the input fields never disappear, only labels do, and the sheet looks like this:

[arbron]

This is because we don't have a prepareBaseCurrencies method similar to what we are doing with skills and abilities to ensure that the proper values are available in character data. I have some plans to try and rework this functionality into the new MappingField so that should make it easier to get this working properly on normal characters, group actors, and containers (though currencies aren't shown on containers yet so no one notices the bug there).