Implement post deployment verification

[hemarkus]

Implement a verification function to check if the deployment was successful.

[jrake-revelant]

this could be related to the introduction of a multi-mode (manifest based deployment). To be discussed when we have a strategy for this ticket.

[jrake-revelant]

The multi-mode might make dependencies between services and times of deployments necessary

[mattthias]

In #23 we added plugin support. We need to create a plugin to check after deployment.