Tasks as Notes as Tasks

As noted in Bug #319143 we want to be able to keep notes :

1) When a task is closed, we want to write stuff about that and keep that task out of the flow but not in the closed pane.
2) We may have an idea that we want to keep without having an action related. Later, we might want to be more precise and transforming that in a task or, adding a list of task related to that idea.
3) You may have a permanent non-task (like "book to read") where you will add a list of things who may be tasks or not ("Guerre et Paix" would be a task because the "read" is implicit)