Add notice to website about running CMake in dev console

[TankOs]

CMake, on Windows, needs to be run from the Visual Studio developer console in order to function correctly (at least for the NMake generator).

There's already a notice in the Building section, but it's missing in the Running CMake section.

[essial]

No it doesn't, as far as Visual Studio is concerned. I specified my SFML install path by setting SFML_PATH to my libraries folder (which is where i built SFML and put the libs/headers into) and SFGUI generated and built just fine. No console needed.

[eXpl0it3r]

It does if you use nmake. If you build a solution file, it's not needed. Also, setting SFML_PATH is the wrong variable, you need to set SFML_ROOT.