Log Message:
update to 1.19.1
changes:
* Make code compatible with python3
* Separation of python module and resources in source package
  (packagers may need to consult INSTALL)
* Move to v2 of PyQt API
* Remove deprecated numpy API from helpers module
* Allow FITS dataset names to be blank if prefix/suffix are not
* New ast-based code security checker
* Picker uses 1-based index for consistency
* Allow non-text datasets to be used for labels
* Add number->text conversion dataset plugin
* Add binning dataset plugin
* Allow more significant figures in float values
* Intelligent choice of significant figures when interactively
  changing axis range
* Decrease minimum range of axis
* Add notes setting to document, pages and graphs
* Add option to disable scaling of marker border with point scaling
* Implement label at-minimum/at-maximum for ternary plot
* Add border and background fill settings for text label widget
* Enable FITS support with astropy
+bugfixes