Merge: inkscape_tools: support Inkscape versions before and after 0.92

Inkscape changed the default DPI at version 0.92. This PR improves `svg_to_png_and_nit` to set the default DPI according to the detected Inkscape version, 90 DPI up until version 0.92 and 96 DPI for version 0.92 and later.

Reference: http://wiki.inkscape.org/wiki/index.php/Release_notes/0.92#Important_changes

This is a more portable solution than #2374.

Pull-Request: #2406