- Add InitSDK() API with no parameters. This API reads server parameters from environment variables, such as fleet ID,
  compute name, WebSocket URL, process ID and auth token. This API simplifies SDK initialization in Amazon GameLift managed EC2 fleets.
  For initialization in Amazon GameLift Anywhere fleets, call InitSDK() with the ServerParameters parameter.
- Provide better error messaging for APIs.
- Remove usage of "std::" in InitSDK() API when -DGAMELIFT_USE_STD is disabled
