Proctor version 2

[jasoet]

Notable Changes:

• Execution Context mechanism, all of the information on a job is stored including logs.
• Ability to fetch logs even the execution process is interrupted (web socket disconnected, etc)
• Plugable Authentication mechanism using go-plugin.
• Refactor code, now purely use go Kubernetes client both for job execution and log retrieval.
• More consistent directory structure.
• Better CLI error messages.
• Prometheus metrics collector
• Notification Plugin (Beta)