Implement the rdc_lib API to support the job stats

Add the function to start and stop the job recording.
Add the function to get the job stats for each GPU and summary of multiple GPUs
Add the function to remove the jobs.

Add a class RdcLogger which can control the log level using the environment variable RDC_LOG.
This is similar to GRPC_VERBOSITY gRPC. When the customer has the issues, he can enable the verbose
log to help us to troubleshoot the issues.

Add the -u support in the rdci group, fieldgroup and dmon for connecting to rdcd without authentication.

Change-Id: I22c591823c1ee6485db106b911bed8271d1b2769

example/job_stats_example.cc

@@ -92,11 +92,9 @@ int main(int, char **) {
         goto cleanup;
     }
 
-    // (2) start the recording. Set the sample frequency to once per second, the
-    // max keep age to one hour and the maximum number of samples to
-    // keep to unlimited.
+    // (2) start the recording. Set the sample frequency to once per second.
     result = rdc_job_start_stats(rdc_handle, group_id,
-        job_id, 1000000, 3600, 0);
+        job_id, 1000000);
     if (result != RDC_ST_OK) {
         std::cout << "Error start job stats. Return: "
             << rdc_status_string(result);