Ability to control alignment in fitSelection() and "zoom in" tool

[tblaette]

Added ability to control alignment in fitSelection() and "zoom in" tool:

• enabled to specify SVGAlignX and SVGAlignY parameters in fitSelection():
  • fitSelection(value, selectionSVGPointX, selectionSVGPointY, selectionWidth, selectionHeight, SVGAlignX=ALIGN_LEFT, SVGAlignY=ALIGN_TOP)
  • refactored fitToViewer() to call the new fitSelection() function internally
• made the zoom in tool to respect the toolbarProps.SVGAlignX/Y props. If for instance toolbarProps.SVGAlignX is set to center, drawing a rectangle to zoom in will now center the selected area in the view.
• updated the documentation to reflect the changes above

Note: if you would like to have typescript support in your project as well, see PR #226