Spice Templates Overview Reorg & Update

cc// @russellholt @jagtalon @jdorweiler @mwmiller 

Made several updates to the template groups in an effort to make them easier to understand and use.

Any feedback/thoughts on this guys?

Note: It seems that there is a difference between Github's handling of underscores, "_", in an anchor's text and the DDG-Docs site: Github keeps the underscores for the anchor's `name` attribute, but our docs do not. These updates make the links work on the DDG-Docs site, so the index is broken on GitHub.