Create an API construct

[jayair]

Make it easier to create APIs by creating a higher level construct. Need to automatically handle things like cold starts, etc.

TODO

• easy way to enable CORS, if both cors and corsPreflight are defined, cors takes precedence
• enable access log by default, allow customizing log format
• enable xray by default for all lambdas
• enable AWS_NODEJS_CONNECTION_REUSE_ENABLED by default for all lambdas
• easy way to enable AWS_IAM authorization for all routes, allow override per route
• easy way to define common Lambda props (environment, policy, srcPath, etc) for all aroutes, allow override per route