WandB Dashboard Support

[IKACE]

Why are these changes needed?

Support WandB dashboard, which collects different metrics in the job and synchronizes stats to the cloud.

• Log job parameters, training metrics, testing metrics, and system stats
• Record raw logs from aggregator and executors
• Optionally checkpointing model weights and backup at WandB cloud

TO DO

• [x] Update README and docs for new WandB dashboard
• [x] Testing on new Tensorflow Jobs
  • [x] TF Cifar 10 (20 training rounds & 1 evaluation round)
  • [x] TF Femnist (20 training rounds & 1 evaluation round)

Checks

• [x] I've included any doc changes needed for https://fedscale.readthedocs.io/en/latest/
• [x] I've made sure the following tests are passing.
• Testing Configurations
  • [x] Pytorch Dry Run (20 training rounds & 1 evaluation round)
  • [x] Pytorch Cifar 10 (20 training rounds & 1 evaluation round)
  • [x] Pytorch Femnist (20 training rounds & 1 evaluation round)