Let user specify amount to send in fiat currency.  Show current exchange rate in status panel.

Send in Fiat:
On Send Screen, user can enter either BTC or fiat (USD, EUR, etc.).  If you enter an amount in one box, the other box will update using the current exchange rate.  This is useful if you want to pay someone a particular fiat amount (eg, $25 USD) without having to manually calculate the equivalent BTC amount.  It uses whatever currency the user has selected in the exchange rate plugin.  If the exchange rate plugin is not enabled, the fiat amount box is disabled.

Show Exchange Rate:
I noticed there was no way to see the current exchange rate like there is in other wallet applications.  This is helpful in case you want to monitor the exchange rate either out of curiosity or to know when is the best time to send bitcoins.  So I appended the current exchange rate to the end of the string in the status panel at the bottom of the window.  It looks like this "  1 BTC = 750.00 USD".  It only activates if the exchange rate plugin is enabled, and it uses whatever currency the user has selected.