FBX: Correct camera position and clip planes.

FBX: Correct camera position and clip planes.

Fbx cameras are stored in the scene graph as well as having separate camera properties.
The separate camera properties have a camera position and direction that is already fully
transformed based on its position in the scene graph so this results in the assimp
camera being transformed twice. Since the scene graph contains all the relevant
transformations the camera position and direction can just use default values. Fbx
specifies cameras along the positive x axis so the default camera values have a up and
direction set accordingly.

Fixes: #807 #643