Merge: nitdoc: introduce tabbed view to hidde less important data

Merge: nitdoc: introduce tabbed view to hidde less important data

This PR introduce discrete tabs in the Nitdoc HTML output to hidde less important data like linearization tree, subclasses list etc.
This makes the main page more clean and readable.

Just pass the mouse over a definition to make the tab menu appear and select the details you want to see.
I also moved the source link here.

One can see the difference on [`Array[E]::SELF`](http://gresil.org/jenkins/job/CI-nitdoc/ws/doc/stdlib/class_standard__collection__array__Array.html#article:standard__collection__array__Array__SELF.definition). Notice the little burger menu on the right of the signature.

Démos:
* [stdlib](http://gresil.org/jenkins/job/CI-nitdoc/ws/doc/stdlib/index.html)
* [nitc](http://gresil.org/jenkins/job/CI-nitdoc/ws/doc/nitc/index.html)

Pull-Request: #1330
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>