* doc: formatting and point to plugin.md

Slight tweaks in CONTRIBUTING.md and point to plugin.md which also has a
bunch of info.
Signed-off-by: Miek Gieben <miek@miek.nl>

* Update plugin.md
Co-Authored-By: Chris O'Haver <cohaver@infoblox.com>

* Add minimize to configuration knobs
Signed-off-by: Miek Gieben <miek@miek.nl>

* more
Signed-off-by: Miek Gieben <miek@miek.nl>