GUI: DoubleDescriptor interfaces ---> DoubleProperty interfaces

DoubleDescriptor-based interfaces are partially replaced by DoubleProperty or by simple double setter method.

Sometimes an additional inheritance is added to reuse the same property for few types.

Non-const interfaces DoubleProperty& were added for future passing to spinbox-serving functions. To the date, the property values are changed via functional pointer set() of DoubleDescriptor. It hides from the reader the real matter of fact which method can do such changes. With explicit references it should become more transparent, but from many lines the const keyword will be removed (this is an announcement).

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 and 3 for DoubleDescriptor