Overhaul of advanced features

Origin of:

- composite types
- one of type
- entity definition
- exclusive properties
- examples folder

Syntax update for:

- one of type
- referencing
- templates properties (variable property name)
> Please put info about this One or many in the README.

`One or many` does not belong to README as it is an MSON entity defined in the [HAL example](examples/HAL.md#one-or-many-one-of-t). Same as `Link`. Those are custom types defined in that example MSON. The fact you haven't spot it makes me worried tho.