Add simple example skeleton to docs

[darksylinc]

It has been pointed out to me that, unlike our 1.x sister, we lack a simple skeleton that with a few lines one can have Ogre running ASAP on screen.

ExampleProject is too complex for that.

That's my fault for thinking 2.x users come from a 1.x background (Ogre setup is almost the same) and trying to be a perfectionist:

The thing about GameEntityManager and co. is that we don't dictate how you want to do things (you can do your render loop how ever you want), but there are many common mistakes and that's what we teach from Tutorial01 to Tutorial06 and why we provide the "SamplesCommon" framework library.

While one could do things whatever way one wants, I found myself several times having to advise users on how to fix: Performance problems, Stutter, high input latency, lack of determinism (which complicates testing, and in the case of certain applications; it completely destroys them); even if single threaded. All things that could've been avoided if the base fundamentals were solid.

But being so perfectionist I forget I need to show first how to get a window on screen with no dependencies.

[darksylinc]

Tutorial00_Basic has been added, now only the documentation needs to be changed to mention it.