How to maintain the UIMA Eclipse update site

The Eclipse update site is a composite update site.  The top level has subsites for
  - UIMAJ SDK
  - RUTA
  - UIMA-AS
  
The update site only needs maintenance if the number of subsites changes.  Normally this is not the case.
See the uima-eclipse-composite-update-site project's "buildCompositeRepository.xml" for details.

Subsites need maintenance, for the following things:

1) removing releases that were buggy and replaced, where there's no value in keeping those releases in the update site.
2) slicing off a bunch of older releases from the main subsite, into an appropriately named archive for those.  This process
creates two subsites
  - the original, but with the sliced of versions removed and
  - a new subsite with the removed versions.
  
  Once promoted to the Apache Mirror system, the new subsite is deleted.  This causes it to be removed from the 
  Apache Mirror system, but it is kept in the apache archive.  
  
  When this is done, please document where the sliced off older releases went (the name of that update site) so people
  wanting to install from there still can do that.
  
How to run
----------

1) update the POM: 
  - change property subsite to "uimaj", "ruta", "uimaj-v3-pre-production", etc.
  - if doing a "slice" operation, set the property "slice" to something like:
    uimaj-2.4.0-2.9.0  indicating the subsite name and the versions included 
2) update the subsiteMaintenance.xml to specify the maintenance tasks