Avoid confusion with RaifTransaction field names

Refactor them to distinguish between source and destination accounts.
Also fix typo inherited from actual CSV field name.

gcconv.py

         (
             transaction_date,
             booking_date,
-            account_number,
-            account_name,
+            src_account_number,
+            src_account_name,
             transaction_category,
-            accocunt_number,
-            name_of_account,
-            transaction_type,
+            dst_account_number,
+            dst_account_name,
+            dst_ransaction_type,
             message,
             note,
             vs,