Add Fiat / IOTA to Balance Menu

[justinchang1124]

The Balance menu in Firefly could be improved by adding a Fiat / USD value. Several users find that going to the Token menu, followed by hovering over the rightmost point, could be made more elegant.

Below is a nondescript proposed implementation. With such a change, the information in the boxed menus (Holdings, Portfolio, Token) would now be symmetric with the information in the Balance menu (current miota, current fiat value, current fiat / miota). Thank you for your time and consideration.