PublicShow -- Store chat messages

Source chat_store(+Message:dict) is det
Add a chat message to the chat store. If Message.create == false, the message is only stored if the chat is already active. This is used to only insert messages about changes to the file if there is an ongoing chat so we know to which version chat messages refer.
Source chat_messages(+DocID, -Messages:list, +Options) is det
Get messages associated with DocID. Options include
Maximum number of messages to retrieve. Default is 25.
Only get messages after TimeStamp
Source swish_config:chat_count_about(+DocID, -Count)[multifile]
True when Count is the number of messages about DocID