Merge pull request #15 from mmoadeli/MAID-60_Merge_Acknowledgement_work_in_routing_to_next

Maid 60 merge acknowledgement work in routing to next
Create group_message_handling.md

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Update group_message_delivery.md
Merge remote-tracking branch 'upstream/next' into MAID-9_Remove_group_leader_semantics_from_Routing
removing group leader from relay handling