en injection on 20130827-050012
fr injection on 20130827-050012
ECMS-5597 Slow loading of symlinks in Content List View

Problem analysis
* When opening a CLV of symlinks (category), we copy all properties of the target node to the symlink node.
  When there is nothing to update, this copy operation is useless and impacts the performance.

Fix description
* Check the last modification date of symlink and its target
* Update symlink's properties only when its target has changes in comparison with the symlink.
  This allows to avoid redundant save operations which are quite expensive.