split the API into 2 - a cmix part and a messenger part

Makefile

api/auth.go

api/client.go

api/messenger/backup.go

api/messenger/messenger.go

api/messenger/notifications.go

api/messenger/precan.go

api/messenger/utils.go

api/params.go

api/permissioning.go

api/precan.go

api/send.go

api/user.go

api/utilsInterfaces_test.go

api/utils_test.go

backup/backup.go

bindings/utils.go

cmd/callbacks.go

cmd/fileTransfer.go

cmd/group.go