This fix tries to address the enhancement discussed in 28735 to add
`--format` for the output of `docker plugin ls`.
This fix
1. Add `--format` and `--quiet` flags to `docker plugin ls`
2. Convert the current implementation to use `formatter`, consistent with
other docker list commands.
3. Add `pluginsFormat` for config.json.
Related docs has been updated.
Several unit tests have been added to cover the changes.
This fix is related to 28708 and 28735.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
1c0d37fa7f