Adds multi-level logging to AWS storage.
- A header that includes a timestamp is added to each line of output.
- The logging level can be set via the SDAPI_LOGLEVEL environment variable.
- a value of 2 will output everything that was previously unconditionally written to std::cout
- lower values will output only what should always be output, e.g. error messages.
- the default value is 0
- Each line is now output to the console by a single stream operation. This yields more readable output in multithreaded programs.