fixing bug #3553 by :
- fixing silverstatistics cron
- strengthening method which determine size of data directory
- throwing exception when a scheduled job fails
bug #4014 :  Modify the pagination mechanism: now the pagination is operated directly in the DAOs. So, a search criterion on the pagination is defined and a new list, to represent a list slice, is introduced to carry the search results matching the pagination criterion (the user profiles or the user groups)
bug #4014 :  Merge branch 'core-5.11.x' of github.com:Silverpeas/Silverpeas-Core into bug-4014