fork.js:
  - New Pipelet class has only one source and one destionation:
    - when one adds more than one destionation, a Tee instance is create to receive all destinations
    - new low-level methods for proper encapsulation, allowing derived classes to accept connections
      or provide alternative implementation:
      - _set_source()
      - _add_destination()
      - _remove_destination()
    - Fork is now a deprecated alias of Pipelet

  - New Tee class is a Pipelet with many destinations:
    - is instanciated automatically by Pipelet when more than one destination is requested on a Pipelet
    - overloads add(), remove(), update(), clear(), _add_destination() and _remove_destination()
    - tee() pipelet allows architects to create explicit tee
    - will eventually become Fork, but this cannot be done before the current Fork is retired

  - Set.remove(): remove uneccesary and statistically questionable optimization

  - Set.make_index_of(): remove extra var.