TableView and Qt 5.12 / Qt Creator 4.8

I finally got around to doing the final merge for QmlBook this year.

I just merged the chapter on the brand new TableView. This let’s you show 2D data tables in an efficient way.

I also merged the version upgrade, so the text should now reflect what is available from Qt 5.12 and be based on menus and screens from Qt Creator 4.8.

During this update of the text, we took the decision not to upgrade all import statements to QtQuick 2.12. Instead, we use different versions in different places. However, the contents of Qt 5.12 is covered.

There are still two things left for the 5.12 branch. The first is to use the new input handlers, e.g. TapHandler instead of MouseArea. The second is to setup a release branch in the CI system so that there is a 5.12 version of the book built separately. I suspect that this will force me to learn more Travis tricks :-)