Rewrite export to CSV dialog

Rewrite the dialog to export tables as CSV file using Qt Designer.

Move the entire export functionality to this dialog instead of
generating the file in the main window.

Add some options for the user to change the layout of the CSV file.

src/ExportCsvDialog.h

@@ -0,0 +1,28 @@
+#ifndef __EXPORTCSVDIALOG_H__
+#define __EXPORTCSVDIALOG_H__
+
+#include <QDialog>
+class DBBrowserDB;
+
+namespace Ui {
+class ExportCsvDialog;
+}
+
+class ExportCsvDialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    ExportCsvDialog(DBBrowserDB* db, QString deflocation, QWidget* parent = 0);
+    ~ExportCsvDialog();
+
+public slots:
+    virtual void accept();
+
+private:
+    Ui::ExportCsvDialog* ui;
+    DBBrowserDB* pdb;
+    QString defaultLocation;
+};
+
+#endif