Update README and project page

Project page updated.

Re-opening this to achieve:

• Reduce the amount of text on the project page to minimum needed to describe the function
• Move the existing use cases and instructions to the contributed module guide → .

There will not be mode code merged into the module, just changes to the presence on d.o.

After consideration, the project page is fine. Better to give people the information they need then and there rather than bump them off to other parts of a site.

Automatically closed - issue fixed for 2 weeks with no activity.