EXPORTS: Create pattern piece groups in SVG file export

[slspencer]

What is needed:
Improve the SVG file export to have pattern piece groups.

Background info:
SVG is a preferred publishing format because these files can be:

• printed with high quality at any resolution.
• zoomed or scaled up or down without losing quality.

Current behavior:
There are no pattern piece groups in our SVG file exports. As a result, it is difficult to select one pattern piece and move it in the document without leaving some pattern piece features like notches, internal paths, or labels behind.

Desired behavior: Each pattern piece should have its own SVG group that contains it's cuttingline, seamline, notches, labels, internal paths. The group's id could be set to the pattern piece name.

Here is a current Seamly pattern SVG export file. Click on the blank space below, it will open in your browser. Save to your drive and open with Inkscape to view the XML organization. In Inkscape, press Ctrl-Shift-X to open the XML view, select each element to compare it to its graphic object in the canvas.