Documentation errors

=== In QxtConfigDialog Class ===

This example is false:

QxtConfigDialog dialog;
dialog.addPage(new ConfigurationPage(&dialog), QIcon(":/images/config.png"), tr("Configuration"));
dialog.addPage(new UpdatePage(&dialog), QIcon(":/images/update.png"), tr("Update"));
dialog.addPage(new QueryPage(&dialog), QIcon(":/images/query.png"), tr("Query"));
dialog.exec();

Correction:

QxtConfigDialog dialog;
QxtConfigWidget configWidget;

configWidget.addPage(new ConfigurationPage(&dialog), QIcon(":/images/config.png"), tr("Configuration"));
configWidget.addPage(new UpdatePage(&dialog), QIcon(":/images/update.png"), tr("Update"));

configWidget.addPage(new QueryPage(&dialog), QIcon(":/images/query.png"), tr("Query"));

dialog.setConfigWidget(configWidget);
dialog.exec();