Issue31

Fix issue #31  zoom in problem:
I rewrite MReleaseZoomIn function in mouseactions.cpp

The calculation is that now first calculate the center, on one click is event position, and in box zoom is MAx1 minus 0.5*DX;
then scale the center point by the scale value. minus half of window size and the origin left/top point.

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Also, the position label on the right down corner is now fixed to work