Submitting new build documentation for building CppSharp / QtSharp

[Hecatron]

First time I've done a pull request I've submitted some new docs just to describe how to build CppSharp and QtSharp, with a couple of gotcha's I've found along the way

Looking at the difference in the solution file, it looks like I might have a higher service pack installed for Studio 2013

[ddobrev]

Merged, thank you for contributing.

[jochumdev]

Nice!