rm DoubleDescriptor from code

The rest of DoubleDescriptor interfaces are replaced to DoubleProperty.

DoubleDescriptor is completely removed.

Steps of Descriptor refactoring:

1. reduce usage of functional pointers set() and get() of DoubleDescriptor
2. move Descriptor functionality to Property
3. use Property instead of Descriptor
4. remove Descriptor from code
5. refactor serialization of Property
6. replace Property macro definitions like DOUBLE_PROPERTY(intensity, Intensity) by explicit member with setter and getter

This MR does (1,3,4) for DoubleDescriptor

GUI/View/SampleDesigner/MaterialInplaceForm.cpp

@@ -113,11 +113,10 @@ void MaterialInplaceForm::createWidgets()
     }
 
     // -- Create UI for magnetization vector
-    VectorProperty mag = material->magnetization();
     const auto setNewValue = [this](double value, DoubleProperty& d) {
         m_ec->setMaterialValue(m_item, value, d);
     };
-    LayerEditorUtils::addVectorToGrid(m_layout, col, mag, setNewValue, true, false);
+    LayerEditorUtils::addVectorToGrid(m_layout, col, material->magnetization(), setNewValue, true, false);
 
     // -- Create UI for material selection button
     auto* btn = new QPushButton("...", this);