qt: GUI for conflicted transactions

- Exclamation mark icon for conflicted transactions
- Show mouseover status for conflicted transactions as "conflicted"
- Don't show inactive transactions on overview page overview

src/qt/transactiontablemodel.h

@@ -53,7 +53,9 @@ public:
         /** Is transaction confirmed? */
         ConfirmedRole,
         /** Formatted amount, without brackets when unconfirmed */
-        FormattedAmountRole
+        FormattedAmountRole,
+        /** Transaction status (TransactionRecord::Status) */
+        StatusRole
     };
 
     int rowCount(const QModelIndex &parent) const;