Updating techbase wiki page according to KF5 policies

[Martin Walch]

Hi,

the techbase wiki says

> If you add #includes for Qt classes, use both the module and class name.
> This allows library code to be used by applications without excessive
> compiler include paths.

Taken from:
https://techbase.kde.org/Policies/Kdelibs_Coding_Style

As far as I have understood so far, this is outdated for KF5 and should now
be made exactly the other way round. So, I have some questions:

* Is <QClass> really preferred over <QtModule/QClass> since KF5?
* What is the reason for this?
* Is that wiki page meant to apply to KF5?
* If it shall apply to KF5 is it safe to update it accordingly?
* Should the coding style for kdelibs from KDE4 be kept around?

Best regards,
Martin Walch
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