Move the internal minion representation to match v1beta3

@ddysher review please, this includes removing the duplicate Labels

Extracted from #1600
Thanks. Yes, we should remove NodeResources at some point.

Where available belongs is a bit tricky. Do you consider BoundPods to be "spec"-like or "status"-like? Available could be considered total - allocated, which is similar. Anyway, I'd like to defer that discussion, but "capacity" is ambiguous, as is.

I made a proposal in #2480.