When closing the last sketch, the window position is saved as default

This allows the use-case with users editing one sketch at a time, that
seems to be the most common scenario:

 1. User position the editor as desired
 2. User close the IDE
 3. User opens the IDE by double clicking on another .ino file
 4. The IDE is opened again at the same position

See #4432

Author: cmaglie

app/src/processing/app/Base.java

@@ -327,7 +327,7 @@ public Base(String[] args) throws Exception {
       boolean showEditor = parser.isGuiMode();
       if (!parser.isForceSavePrefs())
         PreferencesData.setDoSave(showEditor);
-      if (handleOpen(file, nextEditorLocation(), showEditor, false) == null) {
+      if (handleOpen(file, retrieveSketchLocation(".default"), showEditor, false) == null) {
         String mess = I18n.format(tr("Failed to open sketch: \"{0}\""), path);
         // Open failure is fatal in upload/verify mode
         if (parser.isVerifyOrUploadMode())
@@ -528,7 +528,10 @@ protected void storeSketches() {
     PreferencesData.setInteger("last.screen.width", screen.width);
     PreferencesData.setInteger("last.screen.height", screen.height);
 
-    String untitledPath = untitledFolder.getAbsolutePath();
+    // If there is only one sketch opened save his position as default
+    if (editors.size() == 1) {
+      storeSketchLocation(editors.get(0), ".default");
+    }
 
     // Save the sketch path and window placement for each open sketch
     String untitledPath = untitledFolder.getAbsolutePath();