Set default-location for projects to documents-dir.

All export files that are derived from the project (BOM,
nomenclature, etc.) are saved in the same directory by default.
In this context, the standard directories have been grouped
together in qetapp.cpp / qetapp.h so that only one place needs
to be searched for in case of any adjustments.

sources/exportproperties.cpp

@@ -16,8 +16,7 @@
 	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
 */
 #include "exportproperties.h"
-
-#include <QStandardPaths>
+#include "qetapp.h"
 
 /**
 	Constructeur par defaut :
@@ -28,9 +27,7 @@
 	  * la zone exportee est le schema avec son cadre et son cartouche
 */
 ExportProperties::ExportProperties() :
-	destination_directory(
-		QStandardPaths::writableLocation(
-			QStandardPaths::DesktopLocation)),
+	destination_directory(QETApp::documentDir()),
 	format("PNG"),
 	draw_grid(false),
 	draw_border(true),
@@ -85,14 +82,13 @@ void ExportProperties::toSettings(QSettings &settings,
 */
 void ExportProperties::fromSettings(QSettings &settings,
 				    const QString &prefix) {
-	QString desktop_path = QStandardPaths::writableLocation(
-				QStandardPaths::DesktopLocation);
+	QString export_path = QETApp::documentDir();
 	destination_directory.setPath(
 				settings.value(
 					prefix + "path",
-					desktop_path).toString());
+					export_path).toString());
 	if (!destination_directory.exists())
-		destination_directory.setPath(desktop_path);
+		destination_directory.setPath(export_path);
 
 	format = settings.value(prefix + "format").toString();