Have a working model for showing the namespaces in a tree with checkboxes.

The namespaces are currently spit into user and system. Later we might
add recognizing namespaces introduced by specific modules/extensions.

pglab/NamespaceFilterWidget.h

@@ -0,0 +1,35 @@
+#ifndef NAMESPACEFILTERWIDGET_H
+#define NAMESPACEFILTERWIDGET_H
+
+#include <QWidget>
+#include <memory>
+#include <set>
+
+namespace Ui {
+	class NamespaceFilterWidget;
+}
+
+class NamespaceItemModel;
+class PgNamespaceContainer;
+
+class NamespaceFilterWidget : public QWidget
+{
+	Q_OBJECT
+
+public:
+	explicit NamespaceFilterWidget(QWidget *parent = 0);
+	~NamespaceFilterWidget();
+
+	void init(std::shared_ptr<const PgNamespaceContainer> nsc);
+
+	std::set<Oid> getCheckedNamespaces() const;
+
+//signals:
+//	void onFilterChange();
+
+private:
+	Ui::NamespaceFilterWidget *ui;
+	NamespaceItemModel *m_namespaceItemModel = nullptr;
+};
+
+#endif // NAMESPACEFILTERWIDGET_H