Revamped openchange_cleanup.py

This is now usable again.

  - Don't delete password files in mapistoreCleanup()
  - reworked the ldb cleanup and enabled it
  - sql cleanup should now be able to figure out the db info from the config
    regardless of the format used (xml, plist, sogo.conf or GNUstepDefaults)
    (We really need a python plist parser.. the current solution is not elegant)
  - Inform user of missing python packages