Yaml formatting support

[thevpc]

nuts has a minimal support for yaml as output format (along with xml, json, table, etc...)
Nuts has also support for syntax coloring( via NTF) for json, java and bash.
We think it is important to implement a yaml formatter (both print as raw and as colorized).
Using an existing library is offlimit for multiple reasons (NTF is a specific format,...) however this should not be too complex because json formatting is already supported