[Zero] Possibility to create documentation

[lfxgroove]

As part of the idea to get documentation going a little bit better CMake has been integrated with Doxygen (what we use to create documentation) via a helpful post on https://majewsky.wordpress.com/2010/08/14/tip-of-the-day-cmake-and-doxygen/.

After running cmake you now have the additional target

make doc

It will generate documentation of the source code in MaNGOS. For now there isn't much documentation but this can still help get a basic understanding of what derives from where and how things go together. There's also some effort to get documentation going, if you feel like you would like to help out with this just fork the repo, add some documentation and make a pull request!

The created docs will be in [tt]doc/html/index.html[/tt] and can be shown in firefox/ie/chrome/your favorite browser.

In the future the hope is to get this to be available on all cores, but for now it will be on the zero branch of things.