This is for supporting json-based plugins. The great thing about this
change is that it allows us to easily print plugin version numbers in
`plugins list`.
This commit introduces many changes:
- a fully functional minio plugin for local installation
- an almost-functional native k8s deployment
- a new way to process configuration, better suited to plugins
There are still many things to do:
- get rid of all the TODOs
- get a fully functional minio plugin for k8s
- add documentation for pluginso
- ...