Chat Redesign: add LinkRegex global parameter to the chat package, containing the regexp that will look for URLs inside chat messages, so they can be properly formatted as html links.
- rework xotcl-core chat machinery to return its responses through JSON and include information about active users - depend on xowiki instead of xotcl-core only - exploit xowiki "Comet" server push implementation when the browser supports it - reduce code duplication - drop plain HTML chat - reduce hardcoded styling - minor cleanups