Fixes #8136: Add plugin documentation and updated rake tasks.

>Files and factories that represent external resources should be represented by their singular model name, for example the resource for content-hosts is in `content-host.factory.js` and represented by:

Use the single form of the entity for the name of the resource and the filename.  For example, the resource for Content Hosts would be in a file named `content-host.factory.js` and look like this: