Hide/Unhide plans

It is impossible to unhide plans once it is chosen "hide". And it is not possible to delete plans.

It may be useful to add the delete option, because the list of plans can become long with time.

It is also useful to keep of a history of deleted options, so in the future, if needed, we can refind the history of the completed plans to see who was responsible for this plan. It is useful in case of responsability.