Handle pullsecret

[gbraad]

The extension need to properly request the pullsecret when needed and perform basic validation before setting it.

On startup, when no pull-secret is available, the start will be postponed until the user has provided this; a dialog or input will be shown to collect this.

The user should be abel to provide the pull-secret from the configuration before start.

Basic validation is performed to make sure the pull-secret is a valid json message; a simple { and } is sufficient as a first increment.