fixed time bug when merging.
arbitrary slicing: remember last 10 recentering positions for angle calculation instead of last recentering position
Revert "arbitrary slicing: remember last 10 recentering positions for angle calculation instead of last recentering position"

This reverts commit 7e4f48332f5db1a782f4bd57789c5462547ce3c3.
Merge branch 'segmentation' of https://github.com/knossos-project/knossos into segmentation
Merge branch 'segmentation' of https://github.com/knossos-project/knossos into segmentation