Watch zilla configuration for changes and apply automatically

[jfallows]

After zilla is configured and running successfully, support ability to change zilla.yaml and have zilla notice to apply the changes.

Typically this will involve tearing down an existing configuration namespace, and applying the new configuration namespace. This requires tearing down any existing streams for bindings in the old namespace before applying the new namespace configuration.

Note that the new zilla.yaml contents may be invalid syntax, and should then be ignored but with a suitable error message to indicate that the attempted configuration changes were unsuccessful, so that the failure can be detected in the logs.

[bmaidics]

Edit config file using kubectl:
kubectl edit configmap zilla -n <kubernetes namespace>