Improved working of BackupDialog

- improved layout
- automatically switch to output component when start is clicked
- coloured output for succes/error message
- highlighter for pg_dump output that highlights error lines

Note: all output of pg_dump goes to stderr because stdout is reserved for output of the backup data.

pglab/PgDumpOutputHighlighter.h

@@ -0,0 +1,20 @@
+#ifndef PGDUMPOUTPUTHIGHLIGHTER_H
+#define PGDUMPOUTPUTHIGHLIGHTER_H
+
+#include <QSyntaxHighlighter>
+#include <QTextFormat>
+
+class PgDumpOutputHighlighter : public QSyntaxHighlighter
+{
+	Q_OBJECT
+public:
+	PgDumpOutputHighlighter(QTextDocument *parent = nullptr);
+	~PgDumpOutputHighlighter() override;
+protected:
+	void highlightBlock(const QString &text) override;
+
+private:
+	QTextCharFormat m_errorFormat;
+};
+
+#endif // PGDUMPOUTPUTHIGHLIGHTER_H