Metric Prefixes rewrite is complete

The latest version of the metric prefix illustration is live on the main site:

The implementation of the 'show calculations' system is fragile, but it does work. I hand coded much of the interaction rather than create a framework to automate the process. If I find myself showing more calculation step throughs on the site.

As with V0.1 of the covalent bond energy rewrite, the Metric Prefixes illustration is more mobile friendly than earlier work. It scales to fit the page area within a reasonable range.