ExtendedObservableObject and new attribute

[KSemenenko]

Description

I propose to expand the base class with useful functions.

AutoProperty Description

public int FirstProperty
{
	get => GetValue<int>();
	set => SetValue(value);
}

I think that this method of implementation to simplify the work with properties.

Attributes Description

NotifyProperty
DependsOnProperty
that allow you to keep track of property updates and call PropertyChange for related properties

public class MockExtendedViewModel : ObservableObject
{

	[NotifyProperty(nameof(ThirdProperty))]
	public int FirstProperty
	{
		get => GetValue<int>();
		set => SetValue(value);
	}

	[DependsOnProperty(nameof(FirstProperty))]
	public int SecondProperty
	{
		get => GetValue<int>();
		set => SetValue(value);
	}

	public int ThirdProperty
	{
		get => GetValue<int>();
		set => SetValue(value);
	}
}

If you assign a new value to FristProperty, you will also be instantiated by the OnPropertyChanged event for ThirdProperty.

Also trigger events for SecondProperty because it depends on FirstProperty.

@jamesmontemagno If you are interested in this I will do PR
I also have such a small library, and I think that this code can be useful.

[jamesmontemagno]

If you want to put in a PR i would be interested in what it looks like for sure.

[valdetero]

@KSemenenko have you seen the attribute usage in PropertyChanged.Fody?