Added Sequence implementation (minimal).
Added missing library events.
Improved Project api.
Generalized workspace objects update steps and added a way to push a task wich takes the object as parameter.
Sequences do nothing after being updated (they don't have children objects to update).
Worspace presents an api usable only for internal objects, to do some stuffs the backend user should not do.
It will be used first so that new objects can be registered in the workspace.
Added some Workspace implementation:
 - weak registries (only provide the object if it's still alive);
 - completed the update loop (updating all projects in parallel);
 - added a project index to hold open projects;
Added a way to work on workspace objects providing a task accessing it. Needs tests.
Added Workspace unit test and some fixes but still don't compile.