Release 7.4.0: Change of underyling multicast cluster discovery

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In order to perform this kind of change, the following changes are applied to configuration files:

(a) The configuration file mdns.properties is no longer needed and therefore removed
(b) The configuration file messaging.properties is no longer needed and therefore removed
(c) New configuration file mdns-cluster-discovery.properties holding multicast settings

Besides that, the following internal changes are done regarding packaging:

(d) Bundle com.openexchange.mdns is no longer needed and therefore removed from the package open-xchange-core
(e) Bundle com.openexchange.mdns.hazelcast is no longer needed and therefore removed from the package open-xchange-cluster-discovery-mdns
(f) Bundle com.openexchange.messaging is no longer needed and therefore removed from the package open-xchange-core

Please note that during the upgrade of all nodes in the cluster, newly upgraded nodes may not be able to communicate with not upgraded nodes in the cluster. This may lead to volatile distributed data being lost, for example connected users might experience their sessions being expired.