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)
Why are we supporting this? Why can't the users simply do the following:

```
# Address

- (object)
  Description is here! Properties to follow. 

  - Properties
    - street
    - state
    - zip
```