Brief upgrade guide (fix for cloudstax#65)

docs/upgrade/Upgrade.md

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+**AWS**
+
+- Stop all services (*firecamp-service-cli -op=stop-service* command) but *firecamp-manageserver* and *firecamp-catalogservice*
+- Upgrade AWS CloudFormation cluster, by updating it with the current template (can be found at https://aws.amazon.com/quickstart/architecture/cloudstax-firecamp/)
+- Download *firecamp-service-cli* binary for the selected release (for example, *wget https://s3.amazonaws.com/cloudstax/firecamp/releases/1.0/packages/firecamp-service-cli.tgz*)
+- Upon cluster upgrade completion, upgrade each service with the new binary (*firecamp-service-cli -op=upgrade-service* command)
+- Start all services back