Add ability to include custom (hex code) swatch colors#149

Lorenza has the option to add either default automatic web colors or custom images for swatches. But the web color swatches are limited to 140 color names and Shopify can only support custom image files with alphanumeric characters.

It would be nice to have the option to add custom hex code swatch colors, as this will provide support for a wider range of variant names and colors for swatches.