Update Motion tracking docs
Could you check on this Sergey?
@Aaron Carlisle (Blendify), suggest not to split files and rewrite as single patch. It makes it harder to review what you changed. (thats unless you really rewrite everything - but thats not the case here).
File split (without edits) can be committed AFAICS.
Seems this only splits the manual pages and doesn't really update any of the content. For example, in the tracking options there's still KLT/SAD options, which were replaced with the planar motion tracker.
Split is perhaps good start, but would be nice to have actual content update.