Fixed magor bug in all the ProAct.Observable class.

* If unknown namespace of listeners is passed as part of
  the second argument of the ProAct.Observable#update method,
  it is ignored.
* Tests for the ProAct.Observable#update method added.
New helper methods added to ProAct.Utils.

* ProAct.Utils.uuid is used for generating unique uuids.
  Can be used to generate unique ProAct.Registry keys.
* ProAct.Utils.extendClass is used for better extension of
  classes. The parent classes should be created in a special
  manner - there is a spec, showing that. Maybe there will
  be a 'type' method in the future.
* ProAct.Utils.clone is used to clone objects.
  For now it works only for arrays...
* ProAct.Utils.ex is updated to use ProAct.Utils.clone.
* All the new methods have documentation and specs.