Add optional Kafka message headers in tests (apache#227)

This patch adds support for an optional Kafka message header inside of
tests, so that the Avro messages are prefixed with a fixed header in
the Kafka message stream.

Reviewer: Subbu

[PINOT-3198] Part 2 of 2 commits to change SegmentOnlineOfflineStateM…

…odel to contain the new CONSUMING state (apache#211)

Added a configurable option for the controller to change the state model to prepare the cluster for
adding low-level kafka consumers.

Any new clusters created will be created with the new version of the state model, but the servers will
not go through the new states since the controller only updates the IDEALSTATE to contain ONLINE or OFFLINE
states.

Tests:
- Ran integration tests with a version of the server that does NOT have the changes for the new state transitions
  (the clusters in these tests were created with the new state model).
- Manually tested the case where a controller upgrade for a previously created cluster leaves the statemodel
  untouched
- Manually tested that adding the config to turn on the statemodel update works, and updates the state model
  as expected, and we can add new segments and queries work after the update.

Removed dependency on javax.ws.rs in favor of explicitly setting resp…

…onse content type (apache#172)

PR: 172
Approver: jfim, Mayank

Improve schema and segment APIs and docs (apache#164)

Use more specific HTTP status codes for schema and segment APIs,
document the status codes.

Reviewer: Joe

Star Tree Creation: Added check to ensure that time column is preserv…

…ed (apache#165)

before splitting on time for leaf nodes.

Remove array creation in Avro message decoder, replace magic numbers …

…by symbolic constants (apache#155)

Optimize for doc level function in group key generator (apache#150)

Remove the error checking in generateKeyForDocId().
Inline the generateGroupKey function.
The overall performance gain for certain use case is up to 20%.

dimension dropdownon tabular, refactor js, tabular header tooltip, co…

…ntributors delta chart area color (apache#133)

dimension dropdownon tabular, refactor js, tabular header tooltip, co…

…ntributors delta chart area color (apache#133)

dimension dropdownon tabular, refactor js, tabular header tooltip, co…

…ntributors delta chart area color (apache#133)