DP-3 - DistributedLog Operation Primitives

[zhaijack]

This is the master ticket for tracking new dlog primitivies:

• [ ] Introduce LogStatus structure
• [ ] Implement GetLogStatus API
• [ ] Implement RenameLog API #209
• [ ] Implement ListLogs API #211

[zhaijack]

I am trying to pick up the DP-3 to work on.