Added listing of triggers for selected table (not completely finished).

Used slightly different approach. This tab is fully build in source code
using subclasses to adjust behaviour of widgets for reuse in the other tabs.
Uses custom proxy model for filtering triggers for correct table and supporting
out of the box sorting by QTableView.

SqlCodePreview: QPlainTextEditor which sql highlighter and in readonly mode but allows copy.

pglab/SqlCodePreview.h

@@ -0,0 +1,30 @@
+#ifndef SQLCODEPREVIEW_H
+#define SQLCODEPREVIEW_H
+
+#include "PgDatabaseCatalog.h"
+#include <QPlainTextEdit>
+#include <memory>
+
+class SqlSyntaxHighlighter;
+class PgDatabaseCatalog;
+
+class SqlCodePreview : public QPlainTextEdit {
+	Q_OBJECT
+public:
+	SqlCodePreview(QWidget *parent = nullptr);
+
+	/** Sets the database catalog that the syntax highlighter is to use.
+	 */
+	void setCatalog(std::shared_ptr<const PgDatabaseCatalog> catalog);
+
+
+	SqlSyntaxHighlighter *highlighter() { return m_highlighter; }
+private:
+	SqlSyntaxHighlighter *m_highlighter = nullptr;
+	std::shared_ptr<const PgDatabaseCatalog> m_catalog;
+
+private slots:
+	void catalogRefresh(const PgDatabaseCatalog *catalog, PgDatabaseCatalog::RefreshFlags flags);
+};
+
+#endif // SQLCODEPREVIEW_H