unified documentation

[paroj]

I have converted the Ogre manual to markdown so it can be used by Doxygen.
The gain is that you get syntax highlighting in the snippets and automatic links to the API.
See here: https://ogrecave.github.io/ogre/api/1.10/manual.html

However Doxygen only picks up fully qualified names, so often the Ogre:: namespace has to be added, which I did here:
https://ogrecave.github.io/ogre/api/1.1 ... esh-Object

but I did not go over all of the manual, so for example there are no links here:
https://ogrecave.github.io/ogre/api/1.1 ... ripts.html

also some of the manual contents should be folded in the header files so it is more in sync with the actual code.

In case some of you would like to help out and improve the documentation, the sources are in the Docs/src/ subfolder
e.g. https://github.com/OGRECave/ogre/blob/m ... scripts.md

and the full documentation can be built using make OgreDoc