Overhaul documentation

[tiedotguy]

Some of the configuration settings, particularly older ones, are either undocumented entirely, or live only in the change-log.

This should be cleaned up, and every single setting and default documented. [README.md] should contain project information, and refer to other files for documentation, ideally not in the root directory which is already a mess (and something I also want to clean up)

[tiedotguy]

These comments have some notes on architecture / performance / scaling:

• Error when trying to run tester #244 (comment)
• Question: Any plans to add TCP server support?.  #276 (comment)
• Question: Any plans to add TCP server support?.  #276 (comment)

I wanted to wait until clustering was in before doco overhaul, but it's likely to be a while, and I have some spare time now (but not enough to get clustering), so I may start on this with a focus on the perf/arch documentation in the coming days.