[Development] Examples and Demos in qtdoc

[Frederik Gladhorn]

Hi all,

We recently had a discussion in the Qt Company about how we can improve the 
first use experience of Qt and one important aspect are the examples and demos.

We have a lot of examples that are limited by the Qt module they live in, for 
example not making use of ready made buttons in Qt Quick. To allow examples to 
use any Qt module while keeping the build system clean (no cyclic dependencies 
between modules), I'd like to propose using the qtdoc module to gather fresh 
and beautiful examples.

We currently have a few bigger examples already that would fit this category 
and plan to invest more into good looking nice and welcoming examples to give 
new Qt users a positive first impression.

Of course we could create a new repo, but considering that we have an existing 
repo which did contain the demo launcher previously and which is ready to be 
used, I'd propse going with it, while the name is not perfect. It's already 
part of the infrastructure and qt5.git, so this seems like an easy way to go 
forward.

Cheers,
Frederik