Publish new snapshot

[toby-freemarket]

Is your feature request related to a problem? Please describe.
There is not action to Publish new snapshot

Describe the solution you'd like
After pushing packages I would like to Publish a new snapshot with the packages before running the runbook

Describe alternatives you've considered
Had to write our own powershell scripts calling your apis to do this

Additional context
none.

[toby-freemarket]

Think the cli work needs to be done first
OctopusDeploy/cli#165