Feature/revise spec

DO NOT MERGE. FOR DISCUSSION ONLY. @zdne @honzajavorek Please comment.

This PR updates the SPEC based on @zdne and my multiple discussions and refinements.

It also pulls in the current README with some typo fixes. 

@zdne I basically forked and update your branch for this PR into master. Would you prefer I just fork off of master and just create a branch the only adds the spec? Let me know.
Can't this optional be represented better? maybe doing it like this.

_Property Member Type_ → `-` _[Property Name]()_[ `:` _[Value Definition]()_][ `-` _[Description]()_]

NOTE: I used `()` instead of `[]` in the example for the link values.