Cleaned up Exchange Rate plugin: more efficient code and more intuitive names for the get fiat balance/price procedures.  Created new procedure used for updating the fiat balance & price on the status panel.  Enhancement: status panel on bottom left now shows the current BTC price (eg, 1 BTC~573.45 USD).
Streamlined code - modified two procs (get_fiat_status_text and fiat_dialog) to call exchange API only once instead of twice (as recommended by wozz).
Merge pull request #634 from dpdtex/FiatPrice

Show Current Fiat Price in Status Panel