Document plugins used by this theme

[matt-bernhardt]

The Wiki should have a page listing what plugins are enabled, and what they do.

Additionally, if there are changes that we are in the process of making to these plugins, those changes should be listed. If there are plugins that are used on -dev or -test only, and should not be moved to another tier, please note those as well.

[matt-bernhardt]

I've started this process in the Google Spreadsheet that you created, on a "Plugins" sheet.