Two improvements in SemiDenseTracking.cpp - Efficient initialization & Correct pose update

[sunghoon031]

1. Removing the redundancy in the function "resize_points" in SemiDenseTracking.cpp by simplifying the computation of the binary matrix B (used for "initialization" step)
2. Corrected the (inverse compositional) pose update step for improved tracking robustness (and this way it simply makes sense mathematically)