qt: keep a list of requested payments

Keep a list of requested payments in the Receive tab so that a user can
recall previously created requests after closing their windows.

Currently this list is not stored between bitcoin-qt sessions. This can
be implemented later, but it is not clear where it should be stored as
I don't think it belongs in the wallet (maybe in QSettings?)

src/qt/recentrequeststablemodel.h

@@ -0,0 +1,61 @@
+// Copyright (c) 2011-2013 The Bitcoin developers
+// Distributed under the MIT/X11 software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef RECENTREQUESTSTABLEMODEL_H
+#define RECENTREQUESTSTABLEMODEL_H
+
+#include <QAbstractTableModel>
+#include <QStringList>
+#include <QDateTime>
+
+#include "walletmodel.h"
+
+class CWallet;
+
+struct RecentRequestEntry
+{
+    QDateTime date;
+    SendCoinsRecipient recipient;
+};
+
+/** Model for list of recently generated payment requests / bitcoin URIs.
+ * Part of wallet model.
+ */
+class RecentRequestsTableModel: public QAbstractTableModel
+{
+    Q_OBJECT
+
+public:
+    explicit RecentRequestsTableModel(CWallet *wallet, WalletModel *parent = 0);
+    ~RecentRequestsTableModel();
+
+    enum ColumnIndex {
+        Date = 0,
+        Label = 1,
+        Message = 2,
+        Amount = 3
+    };
+
+    /** @name Methods overridden from QAbstractTableModel
+        @{*/
+    int rowCount(const QModelIndex &parent) const;
+    int columnCount(const QModelIndex &parent) const;
+    QVariant data(const QModelIndex &index, int role) const;
+    bool setData(const QModelIndex &index, const QVariant &value, int role);
+    QVariant headerData(int section, Qt::Orientation orientation, int role) const;
+    QModelIndex index(int row, int column, const QModelIndex &parent) const;
+    bool removeRows(int row, int count, const QModelIndex &parent = QModelIndex());
+    Qt::ItemFlags flags(const QModelIndex &index) const;
+    /*@}*/
+
+    const RecentRequestEntry &entry(int row) const { return list[row]; }
+    void addNewRequest(const SendCoinsRecipient &recipient);
+
+private:
+    WalletModel *walletModel;
+    QStringList columns;
+    QList<RecentRequestEntry> list;
+};
+
+#endif