Better document meaning of 'live results' vs 'Retrieve from server'

Problem/Motivation

The UI descriptions for the 'Display live results' and ' Retrieve from server' plugins needs some clarification.

I couldn't understand what the difference was until I searched the issue queue, found an old issue about merging another contrib module, and went to read the project page for that obsolete project!

I think part of the problem is that 'live results' has been kept as the terminology from the merged module.

I *think* I've figured out that the difference is:

- 'live results' means that actual search results are returned -- node titles, in the default configuration for this plugin
- 'Retrieve from server' (and most of the other plugins) means 'suggest search terms'

Steps to reproduce

Proposed resolution