Add list function to dockerctl

New dockerctl functions:
dockerctl list - outputs short name of each
available container
dockerctl list -l - outputs short name, image name,
status, and long container name of each container

Partial-Bug: #1324227

Change-Id: I30646db6d04bf8ff1f232c7e3021d790ec5d566a
Merge "Add list function to dockerctl"