Added pref option to disable the FreeCAD logo in the FCStd file thumbnail

src/Gui/DlgSettingsDocument.ui

@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>500</width>
-    <height>593</height>
+    <height>685</height>
    </rect>
   </property>
   <property name="windowTitle">
@@ -283,7 +283,7 @@
         </property>
        </widget>
       </item>
-      <item row="6" column="0">
+      <item row="7" column="0">
        <layout class="QHBoxLayout">
         <property name="spacing">
          <number>6</number>
@@ -338,6 +338,22 @@
         </item>
        </layout>
       </item>
+      <item row="6" column="0">
+       <widget class="Gui::PrefCheckBox" name="prefAddLogo">
+        <property name="text">
+         <string>Add the FreeCAD logo to the generated thumbnail</string>
+        </property>
+        <property name="checked">
+         <bool>true</bool>
+        </property>
+        <property name="prefEntry" stdset="0">
+         <cstring>AddThumbnailLogo</cstring>
+        </property>
+        <property name="prefPath" stdset="0">
+         <cstring>Document</cstring>
+        </property>
+       </widget>
+      </item>
      </layout>
     </widget>
    </item>

src/Gui/DlgSettingsDocumentImp.cpp

@@ -69,6 +69,7 @@ void DlgSettingsDocumentImp::saveSettings()
     prefSaveTransaction->onSave();
     prefDiscardTransaction->onSave();
     prefSaveThumbnail->onSave();
+    prefAddLogo->onSave();
     prefSaveBackupFiles->onSave();
     prefCountBackupFiles->onSave();
     prefDuplicateLabel->onSave();
@@ -97,6 +98,7 @@ void DlgSettingsDocumentImp::loadSettings()
     prefSaveTransaction->onRestore();
     prefDiscardTransaction->onRestore();
     prefSaveThumbnail->onRestore();
+    prefAddLogo->onRestore();
     prefSaveBackupFiles->onRestore();
     prefCountBackupFiles->onRestore();
     prefDuplicateLabel->onRestore();

src/Gui/Thumbnail.cpp

@@ -106,8 +106,13 @@ void Thumbnail::SaveDocFile (Base::Writer &writer) const
     }
 
     QPixmap px = Gui::BitmapFactory().pixmap(App::Application::Config()["AppIcon"].c_str());
-    if (!img.isNull())
-        px = BitmapFactory().merge(QPixmap::fromImage(img),px,BitmapFactoryInst::BottomRight);
+    if (!img.isNull()) {
+        if (App::GetApplication().GetParameterGroupByPath
+            ("User parameter:BaseApp/Preferences/Document")->GetBool("AddThumbnailLogo",true))
+            px = BitmapFactory().merge(QPixmap::fromImage(img),px,BitmapFactoryInst::BottomRight);
+        else
+            px = QPixmap::fromImage(img);
+    }
 
     if (!px.isNull()) {
         // according to specification add some meta-information to the image