Auto set currency codes on leaf nodes

restricted to the currency window...

When the base currency in Sigma is changed, all leaf components without a specified currency is now assumed to be the new currency.

In this case, Sigma should offer the user to add the old base currency to all such nodes, to prevent prices changing when changing the base currency.

Implementation ideas:

1. Auto ask every time base currency is changed

2. A button in the currency window to assign base currency to all leaf nodes without currency

There should be considerations to how the API would use this as well.