Allow to disable the installation of the documentation and examples

It would be nice to be able to not install the documentation (and examples) in space constrained environment. Indeed, these folders can become huge and are not often use in some cases :

• devs are really often always connected and it can be quicker to google something than using the offline documentation
• examples are not that used in in progress project.

I let to you if these should be installed be default of not, my demand is on adding these two as modules/components meaning that they would become easily installable/uninstallable.