RFE: Alarm monitor

Work items:
1. Fix hardcoded vdu
2. Add Functional test
3. Refactor tosca template for alarm
4. Support scaling in/out at the same time.
5. Support multiple triggers, multi-actions
6. Parameterize alarm configuration (threshold, evaluation, action). it could be nice if users can change alarm configuration with the same template.

An example for multiple triggers:

    - vdu_cpu_usage_monitoring_policy:
        type: tosca.policies.tacker.Alarming
        triggers:
            vdu_high_cpu_usage_with_scaling_out:
                event_type:
                    type: tosca.events.resource.utilization
                    implementation: ceilometer
                metrics: cpu_util
                condition:
                    threshold: 50
                    constraint: utilization greater_than 50%
                    period: 600
                    evaluations: 1
                    method: avg
                    comparison_operator: gt
                action: SP1
            vdu_low_cpu_usage_with_scaling_in:
                event_type:
                    type: tosca.events.resource.utilization
                    implementation: ceilometer
                metrics: cpu_util
                condition:
                    threshold: 10
                    constraint: utilization less_than 10%
                    period: 600
                    evaluations: 1
                    method: avg
                    comparison_operator: lt
                action: SP1
            vdu_high_cpu_usage_with_respawning:
                event_type:
                    type: tosca.events.resource.utilization
                    implementation: ceilometer
                metrics: cpu_util
                condition:
                    threshold: 50
                    constraint: utilization greater_than 50%
                    period: 600
                    evaluations: 1
                    method: avg
                    comparison_operator: gt
                action: respawn