update to 1.17
changes:
* Add new broken axis widget with gaps in the numerical sequence
* Grid lines are plotted always under (or over) the data
* Shift+Scroll wheel scrolls left/right (thanks to Dave Hughes)
* Polar plots can have a "minimum" radius and log axes
* Many more LaTeX symbols added
* Add SAMP/VoTable support (thanks to Graham Bell)
* New shifted-points xy line mode, which plots a stepped line with
  the points shifted to lie between the coordinates given
* Points can be picked to console and/or clipboard
  (thanks to Valerio Mussi)
* Allow reversed ternary plot

(drochner)