Implementation of work sessions (creation and saving)

[diegomigliavacca]

The user has to be able to create new work sessions and save the widget status (widgets which are open, widget configuration, etc.) into a remote triple store. It may involve frontend and backend development.

[diegomigliavacca]

Implemented the session insert.
ca8e683

[diegomigliavacca]

Implemented the list sessions.
e656804

[diegomigliavacca]

Implemented the session loading.
52965d4