Pose Covariance calculation

[hirenpatel1207]

Is it possible to somehow calculate the pose covariances? For calculating them with method described in https://ieeexplore.ieee.org/document/4209579 we need the correspondances, at the moment I did not find on how to get them.

[benemer]

Please have a look at the discussion in #52 and #312.

Currently, there is no plan to integrate this in the near future. However, feel free to contribute by adding this feature!