Blender Git Loki

Camera tracking refactoring:

- Deduplicate patetrn sampling used in esm and lmicklt trackers and
move SamplePattern to image/sample.h - Move computation of Pearson
product-moment correlation into own function in new file image/correlation.h
so all trackers can use it to check final correlation.
- Remove SAD tracker. It's almost the same as brute tracker, with only two differences:
1. It does brute search of affine transformation which in some cases helps to track
rotating features 2. It didn't use common tracker api which probably gave some
speed advantage, but lead to a real headache to use it together with other
trackers leading to duplicated code in blender side.
- Switch blenedr to use brute tracker instead of sad tracker which tracking made
source code much more simple to follow.