adding Point counters

[kouichi-c-nakamura]

This Pull Request changed the behaviour of sliceBrowser.m and AtlasTransformBrowser.m.

1. AtlasViewer shows what mode it is in as XLabel of the axes in response to the arrow keys.
   • There were already command window messages, but this is easier to see the current status.
2. Both AtlasViewer and SliceViewer are equipped with point counters at the right bottom corner.
   • They are only shown during transform points editing mode.
   • The most frequent mistake during this step is placing mismatching numbers of points to the two figures.
3. Behaviour of transform points was changed.
   • They respond better to transitions across slices and loading saved data. Slice point number does not update properly when moving to next slice #62
   • They are only shown during transform point editing mode, responding to the t key
4. Internally, ud.pointHands_for_transform and ud.PointHands are now graphic object arrays rather than numbers.

I meant to make small and incremental pull requests but they were neglected. So I replace my previous pull requests with this inclusive branch. I hope you find these features helpful.