Different feature numbers in first frame

[swordjjy]

I run mono_kitti in same data several times, however I found the feature numbers in the first frame are different and same thing happened for the later frames. I also try initialized by myself to fix the initial camera pose and map-point, but the camera pose of the later frames are also different. Anyone knows the reason?? @raulmur

[naja1987]

please see answers in #45