extracted method to store start zoom coordinate
private class for zoom coordinate
number of exposed zoom methods reduced
added change listener for zoom
some refactoring
changed test for coordinates
Merge branch 'zoom' into exp
replaced update zoom
zoom coordinate calculation based on previous zoom
zoom based on property change
Merge branch 'exp' into 2.2
changed more to assume in case of mouse is not supported
Merge pull request #78 from Mario-S/2.2

zoom based on property change