Blender Git Loki

Modal (aka tripod) solver rework

Several major things are done in this commit:

- First of all, logic of modal solver was changed.
We do not rely on only minimizer to take care of
guessing rotation for frame, but we're using
analytical rotation computation for point clouds
to obtain initial rotation.

Then this rotation is being refined using Ceres
minimizer and now instead of minimizing average
distance between points of point of two clouds,
minimization of reprojection error of point
cloud onto frame happens.

This gives quite a bit of precision improvement.

- Second bigger improvement here is using bundle
adjustment for a result of first step when we're
only estimating rotation between neighbor images
and reprojecting markers.

This averages error across the image sequence
avoiding error accumulation. Also, this will
tweak bundles themselves a bit for better match.

- And last bigger improvement here is support of
camera intrinsics refirenment.

This allowed to significantly improve solution
for real-life footage and results after such
refining are much more usable than it were before.

Thanks to Keir for the help and code review.