Expand on shell commands for detailed insight

Was talking over how to build some tests with romil.choksi, and what kind of information we capture and expose via some more shell commands.

• Current SpaceQuotaSnapshots that the Master sees
• Current SpaceQuotaSnapshots that a RS sees (or all RSs)
• Current SpaceViolationPolicyEnforcements that a RS has enabled

We can build out on the status command, with some options for different levels of detail, perhaps. Shouldn't be too tricky – we have the info, just need to wire up java API, RPC, and shell command.