Adding lifecycle hooks to deis-controller api

[Cryptophobia]

Adding the lifecycle hooks feature to the deis-controller api. This allows users to attach lifecycle postStart and preStop hook commands to kubernetes api via the deis api.

Example of a preStop hook that would gracefully shutdown Resque worker processes:
https://gist.github.com/Cryptophobia/447ecea7858d26141359b22161e70ee2

Example of the POST to deis.$hostname/v2/apps/testing-again/config:

JSON Body:

 "lifecycle_pre_stop": {
        "worker": "echo 'Running the postStop script' && chmod +x bin/kube-resque-pre-stop.sh 
&& ./bin/kube-resque-pre-stop.sh;"
    }

For long running preStop hooks the terminationGracePeriodSeconds needs to be increased for the worker pods:

deis config:set KUBERNETES_POD_TERMINATION_GRACE_PERIOD_SECONDS=900 -a testing-worker

The tests are not written yet.
Code in deis-cli has not been written yet.

[Cryptophobia]

This PR is related to this upstream PR:

deis/controller#1311