Initial commit for Rest-Netty Voldemort Server

- Implemented a rest specification for handling get, put, getall, delete
- Uses InMemory Store for now
- Tests coming soon
Fixing get version
Minor changes in message headers and handling non existing keys. Also adding curl tests.
- Fixed message headers in multipart responses
- Changed ETag response headers to X-VOLD-Vector-Clock
- Handled non exisitng or null keys. Sent error message to Client
- Added curl test cases that test REST spec and basic functionalities
Modified parsing and error handling mechanism
- split RestServerDeleteRequestErrorHandler into two classes.
    1) RestServerDeleteErrorHandler and 2) RestServerDeleteRequestValidator
  Repeated this for all other operations

Added  config  parameter specific to the Rest Server
- number of netty boss threads
- number of netty  worker threads
- numer of storage threads in the Rest Server storage thread pool
- queue size in the Rest server storage thread pool
- modified RestService, RestPipelineFactory to incorporate config param
  changes

Added methods in CoordinatorUtils to serialize and deserialze multiple
vectorCLocks

Added origin timestamp and routing type headers to R2Store

Added Execution handler to Netty pipelinne
- submits time consuming channel events to disk access to a seprate
  thread pool
- StorageWorkerThread defines thread in the storage threadpool
- VoldemortStoreRequest is the message event  passed from  VoldemortRestRequestHandler and StorageExecutionHandler
Adding unit tests
- RestServerProtocolTests : protcol tests that validate spec using
  HttpURLConnection to send requests
- RestServerAPITest : basic API test using R2Store to send requests
Minor fixes post code review
- Adding new config for REST Server and reverting changes to the single_node_cluster/config
- Adding a new constructor for R2Store to pass RoutingTypeCode as a constructor parameter
- Renaming Rest service config parameters in VoldemortConfig
- Adding logger.error for all error messages

minor fixes post code# On branch master
Minor fixes post code review. Amending for few missing files in previous
commit.
- Adding new config for REST Server and reverting changes to the
  single_node_cluster/config
- Adding a new constructor for R2Store to pass RoutingTypeCode as a
  constructor parameter
- Renaming Rest service config parameters in VoldemortConfig
- Adding logger.error for all error messages
updating R2Store and RestServerAPITest to push into voldemort/master
moving RestSpecAndBasicUnitTest to test/unit/voldemort/server/rest