CPSPortlets - portlet override (draft)
======================================
Authors:
  - Jean-Marc Orliaguet <mailto:jmo@ita.chalmers.se>

BACKGROUND
----------
The portlets located in a folder are by default visible in all sub-folders.
It means that the amount of portlets tends to increase as one goes deeper into
the site structure.

It can sometimes be useful to control the visibility of the portlets located
in the parent folders.

The solution is to allow users to override portlets.


IMPLEMENTATION
--------------
The implementation is based on a dialogue between the manager(s) of a given
folder and the manager(s) of sub-folders:

- Portlets can be overriden be default unless the 'disable_override' flag is
  set.

- If a portlet located in a given folder has the 'slot_override' flag set then
  only the portlets of the same slot located in the folder and in the folders
  below will be visible. All portlets above except the ones with the
  'disable_override' flag on will be invisible.

- Only visible portlets may override other portlets.


EXAMPLE:
--------

  ::

      Portlet A1 in /workspaces               Portlet A2 in /workspaces
      in SLOT1                                in SLOT1
      -------------------------               -------------------------
      disable_override: YES                   disable_override: NO


      Portlet B in /workspaces/members/user
      in SLOT1
      -------------------------------------
      slot_override: YES


* Visible in /workspaces (SLOT1): A1, A2

* Visible in /workspaces/members/user (SLOT1): A1, B
  (A2 is overridden, A1 cannot be overriden)
