Add ReliableKafkaReceiver in Kafka connector to prevent data loss if WAL in Spark Streaming is enabled. Details and design doc can be seen in [SPARK-4062](https://issues.apache.org/jira/browse/SPARK-4062).

Author: jerryshao <saisai.shao@intel.com>
Author: Tathagata Das <tathagata.das1565@gmail.com>
Author: Saisai Shao <saisai.shao@intel.com>

Closes #2991 from jerryshao/kafka-refactor and squashes the following commits:

5461f1c [Saisai Shao] Merge pull request #8 from tdas/kafka-refactor3
eae4ad6 [Tathagata Das] Refectored KafkaStreamSuiteBased to eliminate KafkaTestUtils and made Java more robust.
fab14c7 [Tathagata Das] minor update.
149948b [Tathagata Das] Fixed mistake
14630aa [Tathagata Das] Minor updates.
d9a452c [Tathagata Das] Minor updates.
ec2e95e [Tathagata Das] Removed the receiver's locks and essentially reverted to Saisai's original design.
2a20a01 [jerryshao] Address some comments
9f636b3 [Saisai Shao] Merge pull request #5 from tdas/kafka-refactor
b2b2f84 [Tathagata Das] Refactored Kafka receiver logic and Kafka testsuites
e501b3c [jerryshao] Add Mima excludes
b798535 [jerryshao] Fix the missed issue
e5e21c1 [jerryshao] Change to while loop
ea873e4 [jerryshao] Further address the comments
98f3d07 [jerryshao] Fix comment style
4854ee9 [jerryshao] Address all the comments
96c7a1d [jerryshao] Update the ReliableKafkaReceiver unit test
8135d31 [jerryshao] Fix flaky test
a949741 [jerryshao] Address the comments
16bfe78 [jerryshao] Change the ordering of imports
0894aef [jerryshao] Add some comments
77c3e50 [jerryshao] Code refactor and add some unit tests
dd9aeeb [jerryshao] Initial commit for reliable Kafka receiver