* Phase list command lists phases of current documentset/plan in
table or yaml format.
airshipctl phase list
airshipctl phase list --plan planName
airshipctl phase list --plan planName -o yaml
airshipctl phase list --plan planName -o table(default format)
Relates-To: #358
Co-Authored-By: Niharika Bhavaraju <niha.twinkle@gmail.com>
Change-Id: I37add2fc9dca2433de525bac8c2cc9e56fe39621