Doc: Adjusting "Core Internals" and children documentation's links

-moved the links out of the paragraphs and into lists because
 the links with the visible text creates confusion
-fixed other links so they point to the correct material.

Task-number: QTBUG-32173
Change-Id: I390aece0aef599fb841730392ced70665fc4f523
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Sze Howe Koh <szehowe.koh@gmail.com>