Add SerializationContext to ICustomSerializer

[axunonb]

Serialization Context

Added a serialization context when invoking CustomSerializers (#167)

• Added a serialization context when invoking CustomSerializers
• Feature/initial step single responsibility principal (Feature/initial step single responsibility principal #168)
• Added regions to help make the YAXSerializer more readable.
• Single Responsibility Principal, moved logic related to creating a custom serializer to it's own class.
• Single Responsibility Principal, moved all or at least most logic related to namespaces to it's own class.
  Co-authored-by: bob.sanders bob.sanders@valtech.com
• Fixes Support ISerializer<BaseType/Interface> of Concrete types #166 ICustomSerializers may have an interface as the generic argument (ICustomSerializers may have an interface as the generic argument #169), e.g.
  public class SomeSerializer : ICustomSerializer<ISomeInterface> { //... }

Custom Serialization bug fixes

• Fix: ICustomSerializer was only called after first deserialization
  • Reasons:
    • In YAXSerializer, HasCustomSerializer was tested BEFORE analyzing the RealType attribute, to it was not called for deserialization
    • At the same time, the default deserialization gave the correct result
  • Measures:
    • HasCustomSerializer is tested AFTER analyzing any RealType attribute
    • Tests will now fail, if ICustomSerializer is not called

[axunonb]

These changes are the precondition for working on #93, #163, #165 (eventually also #84)

[304NotModified]

Nice work :)