Merge branch 'hotfix'
Set sans-serif as default font for text elements

Set sans-serif as a fallback font for text elements. sans-serif is part
of the SVG spec and should be included in any SVG renderer. This might
also fix the [CANT] error in Illustrator.
Merge branch 'master' into hotfix
SVG file chooser expects *.svg file name

Added an extension filter to the file chooser for SVGs.
Added math for bezier approximated concordia lines
Finished basic concordia reimplementation

The Wetherill concordia is now composed of a series of Bezier curves.
The Tera-Wasserburg is implemented in the codebase but not available to
the user, as I still need to implement the axis switch.
Merge branch 'bezier-math' into dev
Merge branch 'hotfix' into dev