Support text in different encoding in Browse Data tab

When browsing and editing a table in the Browse Data tab allow the user
to change the assumed encoding of the text in the table. We'll then try
to convert from this encoding to Unicode for display purposes and to
convert from Unicode to this encoding for editing purposes. This way the
UI and all tools will keep using Unicode while the database format is
still respected. I hope the amount conversions generated this way won't
affect the performance too much.

See issue #414.

src/sqlitetablemodel.h

@@ -12,7 +12,7 @@ class SqliteTableModel : public QAbstractTableModel
 {
     Q_OBJECT
 public:
-    explicit SqliteTableModel(QObject *parent = 0, DBBrowserDB* db = 0, size_t chunkSize = 50000);
+    explicit SqliteTableModel(QObject *parent = 0, DBBrowserDB* db = 0, size_t chunkSize = 50000, const QString& encoding = QString());
     void reset();
 
     int rowCount(const QModelIndex &parent = QModelIndex()) const;
@@ -40,12 +40,13 @@ public:
 
     bool isBinary(const QModelIndex& index) const;
 
+    void setEncoding(QString encoding) { m_encoding = encoding; }
+    QString encoding() const { return m_encoding; }
+
     typedef QList<QByteArray> QByteArrayList;
 
     sqlb::ForeignKeyClause getForeignKeyClause(int column) const;
 
-signals:
-    
 public slots:
     void updateFilter(int column, const QString& value);
 
@@ -57,6 +58,9 @@ private:
     QStringList getColumns(const QString& sQuery, QVector<int>& fieldsTypes);
     int getQueryRowCount();
 
+    QByteArray encode(const QByteArray& str) const;
+    QByteArray decode(const QByteArray& str) const;
+
     DBBrowserDB* m_db;
     int m_rowCount;
     QStringList m_headers;
@@ -82,6 +86,8 @@ private:
     size_t m_chunkSize;
 
     bool m_valid; //! tells if the current query is valid.
+
+    QString m_encoding;
 };
 
 #endif // SQLITETABLEMODEL_H