Issue #171

server limit the number of webUI clients that can attach.

This will probably always be "0" or "unlimited", but allows ops to set a max limit for WebUI clients. (realistically, probably 3 is more than enough)

@crankycoder r?
Not sure if you want to move `document_root` up or down, so the `ws.*` properties are nicely clustered. Or not. But now neither of us will be able to unsee and we can see whom's OCD can outlast whom's.