Log Message:
update to 1.16
changes:
* Experimental MathML support
* Add upper/lower-left/right arrows
* Add options to clip text/lines/shapes to graphs
* Add stacked-area option to bar plot widget
* Draw stacked bar plots top-down for better overlapping line behaviour
* Axis labels can be placed at left or right of axes, in addition to centre
* Line widget now has length-angle or point-to-point modes. Better support
  for only specifying some coordinates.
* Exception dialog records more detailed traceback
* Use top level windows for non-modal dialogs, giving minimize in window
  and no always-on-top behaviour
* Zero length vectors and arrows in vector fields are not plotted
* Add support for strings to be translated
* Add "Sort" dataset plugin
* Add "Histogram 2D" dataset plugin
* Add "Divide by Maximum" and "Normalize" dataset plugins
* Support for *args and **kwargs for custom functions
* Custom colormaps can be defined in the custom editing dialog