New Features

Entity Relations
Added serialization for Entity with EntityPointer. Added the EntitySmartPointer trait that works similar to how serde serializes smart pointers like Box and Rc.
Projection for Option, Vec and Map
ProjectOption, ProjectVec and ProjectMap can be used to serialize containers that contains SerdeProject types or
types that can be Converted to SerdeProject types.
Cow version of TypeTagged
Added support for custom clone-less serialization using TypeTagged.

Changes

ChildMap no longer requires Eq and will keep duplicate keys.

ProjectVec has been reworked.