Add camera system & component

[bkloster]

Currently, the camera is hard-coded in OgreEngine::Implementation::setupCamera. To make the camera properties scriptable, a CameraComponent should be created to enable entities to become cameras. The CameraComponent should have at least the following properties:

Ogre::Real nearClipDistance;
Ogre::Real farClipDistance;
Ogre::ProjectionType projectionType;
Ogre::Radian fovY;
Ogre::Real focalLength;
Ogre::Real aspectRatio;

The accompanying CameraSystem should create an Ogre::Camera if necessary and apply the above settings, together with position and orientation from a TransformComponent.