Additional backend: Add MySQL support?

[abronan]

docker#180 adds MySQL support for libkv.

Additional stores should be treated with care as this leads to more maintenance and an increased pressure to fix bugs. Although if people are interested in having MySQL support, I could carry the PR or contact the contributor from the upstream repository to include it here.

[lrita]

In my opinion, as unnecessary, all the backends get the same treatment. We can separate them into essential backends and optional backends.

We just take more maintenance for the essential backends.

Just like linux, I think the maintainers cannot take care of all architectures well. They need contributors to do some work for the non-mainstream architectures.☺

[abronan]

Thanks for commenting on this repo :) makes sense to me, would you be interested in submitting the PR here for review?