Add back workflow list saving

There should be a "save workflow participants" feature. It implies:

• a button "save this list" on top of the tasks table (and a text input field).
• a drop down list that lists the existing particpants, and a button "load this list" and a button "delete this list". Those controls should be place on the right of the participants selection field (the autosuggest control).

*The "load this list" button has for consequence to create new tasks below the one the user would have already manually set. The tasks newly added will only have their participants, (user(s) and/or group(s)), but directive and limit date will be empty. As a consequence following jira task : (TOBEADDED) should also be achieved at the same time as this one), so that user can edit the values if he wants to set them.

*The delete button, after a confirmation (javascript is enough), deletes the selected list.

once done, list should be saved in abandon* selenium tests, and reused in reviewOk selenium tests.

see if lists should be saved as document models so that they can be shared by users.
this should go in a new module.