Allow a message to be used as source for a new tracker Task

[timbl]

• In the Tracker settings pane, add a feature to select a Tracker connected with the chat
• Add a the Task icon (grey-checked box) to be action toolbar
• When you click/press on it:
• Offer a choice of destination trackers, including ones from the user's type indexes
• Create a new Task in the selected Tracker, whose message is the message contents linked to the URI of the chat message.
• Link the chat message to the Task using a triple in the chat file
• Link the chat message to the Task using the same triple in the task state file
• Leave the Task icon selected (like selected thumbs up) in the toolbar
• Link that task icon to the task to the user can always find the task.