added Vector2, Vector3, Matrix3, ColourValue, Quaternion and String to the misc folder as header files
(each of them contains #include <string> … typedef std::string String , etc.)
please use String from now on by including <misc/String.h"
removed #include <OgreVector3.h", etc. from "CoreIncludes.h" (adjusted all source files)
adjusted all the source files (except network, that keeps <string> for the moment) (what a mess..)
moved usleep hack to misc/Sleep.h
relative include paths for files from other root directories (like misc, network, etc.)
(but it stills writes "../Orxonox.h" when in folder orxonox/objects)
"OgreSceneManager.h" —> <OgreSceneManager.h>
included OrxonoxPrereqs in every file in folder orxonox
moved HUD and ParticleInterface to namespace orxonox
removed some using namespace Ogre/std when appropriate