Add serverless/EKS options in node backend

[bmonkman]

Coordinate with commitdev/zero-aws-eks-stack#231 to add option to zero module.
Add basic code to enable the node backend to function either as a lambda function or locally.
Add initial SAM code to allow manual deployment to multiple environments
See https://github.com/commitdev/sam-test/tree/node-backend-with-db-and-xray for examples