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)
I understand that `(one of)` is for values and `One of` is for keys. But why can't we use `(one of)` for both of them? The machine can understand what the case if depending on where they occur.