Proposal: Define a job type to track all kinds of jobs on the same cluster

[MartinForReal]

It would be better if we can apply a single set of rules to all of jobs running on the cluster regardless of jobs' types.

Following information should be considered if we define an job type:

• roles and specs:
• policy
• Owner/Origin(e.g. tfjob, mpijob)
• status optional:
• queue/quota
• scheduling profile

We can see similar pattern in storage management, cluster management. e.g. Machine and vendor-spesific machine type pvc and pv

[gaocegege]

Please have a look at https://docs.google.com/document/d/1x1JPDQfDMIbnoQRftDH1IzGU0qvHGSU4W6Jl4rJLPhI/edit

[Jeffwan]

@MartinForReal Feel free to check issues with "help wanted" tags and any contribution are welcomed.