Doc: list Qt Essentials, Qt Add-ons, and Qt Tools
Doc: list Qt Essentials, Qt Add-ons, and Qt Tools

Create separate tables for each category.

Change-Id: I0d461feb1a14cfc16914e1ace0c5204a8a3e1d78
Reviewed-by: Jerome Pasion <c10995d24f6b454503389e8d00d837aef038985d@nokia.com>

kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc