* Remove node's main identitiy from NodeInfo.
Preparation for getting rid of services + supporting multiple identities
on the node.
NodeInfo keeps multiple identities as a list. For now the first one is treated as a special one.
Introduced function chooseIdentity in CoreTestUtils as a preparation for proper handling of multiple identities in the future.
Remove legalIdentityKey from ServiceHub, add extension function - chooseIdentity on ServiceHub.
Add `me` field on FlowStateMachineImplemetation, flows should know what the calling identity is.
Remove SERVICES_PREFIX in artemis messaging layer.
* Address minor comments.
* Fixes after rebase.
Remove chooseIdentity from ServiceHub
* Rename me to ourIdentity on FlowLogic
* Fixes after rebase
* Address Ross comments, fixes
* Fix after rebase
* Fix services certificate paths
Apply Patrick's patch.
