Streamline usage of humaneimage-model.lib.js

[yveszoundi]

Background

• Initially the set of "humaneimage" scripts only supported images (PNG/SVG) export.
• Now there's also an export function to PowerPoint (pptx format), to allow non technical people to reuse/modify easily diagrams. The code of humaneimage-model.lib.js is used for PowerPoint export, it's based on humaneimage.lib.js.

Problem

humageimage-model.lib.js and humageimage.lib.js need to be kept in sync, which creates maintenance issues.

Proposed solution

Reuse humaneimage-model-lib.js for exporting images, instead of redundant logic.

• "Crawl" the "model" to populate the SVG string
• If PNG export was requested, convert the SVG to PNG