Expose the CameraGroup near, far, and near/far boundry as properties

Expose the CameraGroup near, far, and near/far boundry as properties

The near/far boundary, called "near-field", can be set to 0 which
disables the far camera and renders the whole scene using only one
camera. I'm hoping that this may be useful in resolving some
system-specific rendering bugs.

Various fixes were made to correctly render the scene using only the
near camera.