Adding a log file option for the chat

Makes it easier to debug afterwards. Remember to name the log file to suit your needs in config.json
Adding example logging configuration
Continue work on issue #15 - clients can enter a paused room
Add configurable full room link
Adding feedback URL to admin UI
Adding fullRoomLink to config.json example
Adding function to check for counselor presence in room

To make it possible to prevent clients entering rooms without counselors
Adding clearification comment