Depth ray correspondences

During point alignment, correspondences are searched for in the other camera views. The best match, along with a confidence value, is used to adjust the depth value in order to fuse together all the camera viewpoints. Currently correspondences are searched for using a square window around the reprojection location in the other camera view. Instead, since only the depth can vary if camera pose is assumed fixed, only search a ray (line) through the image along the original depth axis. This will both vastly reduce the number of points tested but also would be expected to produce a better result by not allowing correspondences off axis.