version 2.4

Please also look at opm-core 2.4 changelog.

• Add ability to merge two services (not exposed in the UI)
• Fix perl 5.10 compatibility
• Fix forgotten translations
• Fix ACL on wh_nagios.hub_reject table
• Handle perfdata file with empty perfdata.
• Make sure grant_dispatcher allows user to call dispatch_record()
• Don't truncate metric table on duplicate key, allowing easy dump/restore of the data
• Activate automatic data purge