Add preconfigured monitoring dashboards

[mskrajnowski]

Add CloudWatch dashboards for monitoring:

• ecs instance metrics, eg. instance count, cpu usage, memory usage, cpu available, memory available, task count feat(ecs): cloudwatch metrics and dashboard widgets #73
• ecs/host_group autoscaling group and instance metrics, eg. instance count, cpu usage, memory usage, cpu available, memory available feat(ecs/host_group): cloudwatch metrics and dashboard widgets #69
• ecs/network global load balancer metrics, eg. number of requests, number of requests by response code, response time feat(ecs/network): cloudwatch metrics and dashboard widgets #71
• ecs/services/web target group load balancer metrics, same as for ecs/network feat(ecs/services): cloudwatch metrics and dashboard widgets  #67
• ecs/services/* service metrics, eg. task count, cpu usage, memory usage feat(ecs/services): cloudwatch metrics and dashboard widgets  #67
• rds/postgres database metrics, eg. cpu, memory, disk usage, query count, query time, number of connections
• elasticache/redis database metrics, similar to rds/postgres
• ses/domain sent emails metrics, eg. email count, bounce count, bounce rate feat(ses/domain): cloudwatch metrics and dashboard widgets #75