Implementing Server-side Stores for Write Operations

This review is getting quite big, so I'm going to cut it off here at a working point. Code is to be merged into a separate branch (not voldemort/master)

Includes:
- PUT and DELETE workflow working through VeniceStore
- Included configuration by store, rather than by node
- Cleaned up code as per Sid's and Felix's comments

Not Included:
- Offset Management
- Throttling
Shouldn't we make this a no-op?

I don't want regular (i.e.: RPC) put requests to infiltrate a VeniceStore. The RPCs should make their way here in the first place, so that should be handled at another level, but I think it wouldn't hurt to have an extra level of safety by making this a no-op (perhaps accompanied by a loud scream in the logs).

Making this a no-op means we should create another put API which would be known only by the VeniceConsumerTask.

Let me know if you had other plans regarding this?