Display float values with btcctl with %f.

This commit modifies btcctl to show float values with %f instead of the
default %v.  This means the values will show similar to 1180923195.260000
instead of 1.18092319526e+09 (scientific notation).

util/btcctl/btcctl.go

@@ -110,7 +110,7 @@ func displayGeneric(reply interface{}) error {
 // is returned if a float64 is not passed.
 func displayFloat64(reply interface{}) error {
 	if val, ok := reply.(float64); ok {
-		fmt.Println(val)
+		fmt.Printf("%f", val)
 		return nil
 	}