Mitosis editing doesn't push to end, however reseg will now extend leaf tracks.

src/MATLAB/+Editor/CreateMitosisAction.m

src/MATLAB/+Helper/CheckInTracks.m

src/MATLAB/+Segmentation/+ResegFromTree/FindFrameReseg.m

src/MATLAB/+Segmentation/+ResegFromTree/FixupSingleFrame.m

src/MATLAB/+Segmentation/+ResegFromTree/GetTrackInEdge.m

src/MATLAB/+UI/FigureCellUp.m