JSON swatch list

This change uses a new JSON file to list all swatches statically. While I have not changed much in terms of using the new swatch list yet, it should be easy. Currently, I just have the Gruntfile updating the `swatch` task config based on the contents of the JSON file.

If anyone is interested in seeing new grunt tasks for updating files based on the swatch file (for example, file lists in files like `composer.json`), let me know and I may try it out.