Wiki and instructions on attributes

[Legendami]

The wiki should be updated with the following information:

• Introduction about the libraries that we combine.
• Guide on how to run the BooksQL application (API).
• Introduction how GraphQL implementation works.
• More walkthrough on how to use GraphQL in general for beginning developers
• Introduction how REST work.

Extra

• Advanced scenario's (how to extend the library)
• How to Debug.