Merge branch 'simulation'

Merge branch 'simulation'

- splitted expand, performance improvements and bugfixes
  (see commit 5c09e2e272003a32c584e7d2df9aa62d270ee2e6 for more information)
- Zope: monkey-patch 'transaction' to provide start time of transaction
- CMFActivity: new 'merge_parent=<path>' SQLDict parameter
- CMFActivity: try to reserve older messages first (ORDER BY priority, date)
  (see commit 275799fee81638c365e07303f7465421d7669cef to update existing
   activity tables)
- drop legacy simulation