Create dedicated framework integration examples

[mwestphal]

Context
the libf3d can be used for a quick and easy 3d viewer, but how can it be integrating into existing framework ?
Let's create example showing how to.

Suggested solution
Create dedicated framework integration examples, demonstrating how to integrate the libf3d with well known open source frameworks such as Gnome, KDE or Unity

There is an existing code, Exhibit, that integrates libf3d into Gnome using python: https://github.com/Nokse22/Exhibit

Related to: #1670