Completed the interface documentation of Workspace.
Added some documentation to WorkspaceObject but will finish later.
Simplified WorkspaceObject on_next_update signature.
Boost  future.then() don't work yet... also we can't be sure it's safe to pass a reference in a future to an object we, in theory, are not sure is still alive.
Passing a shared_ptr would destroy the encapsulation of the Workspace.