Remove external dependencies from mlperf_logging so it can run in standard Python3

[ar-nowaczynski]

It would be a major improvement in the usability of the mlperf_logging module if it had no external dependencies beyond those available in the Python 3 standard library. There will be no need for installation. Just clone the repo and run the checkers.

I volunteer to work on this and create pull request if owners give it a green light.

[arjunsuresh]

@ar-nowaczynski I'm not fully familiar with this repository. But I see that it has a logging library, result/compliance checker and then the result summarizer for training. Are you talking about separating them to different packages?

Currently pip install mlperf_logging works but it does install external packages like pandas as they are listed as dependencies.