Adjust Mockup display of SVG based on project's wxWidgets version

[KeyWorksRW]

Description:

wxUiEditor is using lunasvg to display SVG files in the Mockup panel. Unless the dev has stated they are using wxWidgets 3.3, that display could potentially be wrong. Or rather, the image might display correctly in the Mockup panel, but not correctly when the user displays the SVG file in C++, wxPython, or wxRuby.

If the dev specifies wxWidgets 3.1, SVG should not display at all. If 3.2 is displayed, SVG should be displayed using nanosvg. If 3.3 is displayed, SVG should be displayed using lunasvg.