qt history view custom fiat input fixes

previously, when you submitted a fiat value with thousands separator,
it would be discarded.

electrum/exchange_rate.py

@@ -464,9 +464,13 @@ class FxThread(ThreadJob):
         d = get_exchanges_by_ccy(history)
         return d.get(ccy, [])
 
+    @staticmethod
+    def remove_thousands_separator(text):
+        return text.replace(',', '') # FIXME use THOUSAND_SEPARATOR in util
+
     def ccy_amount_str(self, amount, commas):
         prec = CCY_PRECISIONS.get(self.ccy, 2)
-        fmt_str = "{:%s.%df}" % ("," if commas else "", max(0, prec))
+        fmt_str = "{:%s.%df}" % ("," if commas else "", max(0, prec)) # FIXME use util.THOUSAND_SEPARATOR and util.DECIMAL_POINT
         try:
             rounded_amount = round(amount, prec)
         except decimal.InvalidOperation: