[SPARK-1341] [Streaming] Throttle BlockGenerator to limit rate of data consumption.

Author: Issac Buenrostro <buenrostro@ooyala.com>

Closes #945 from ibuenros/SPARK-1341-throttle and squashes the following commits:

5514916 [Issac Buenrostro] Formatting changes, added documentation for streaming throttling, stricter unit tests for throttling.
62f395f [Issac Buenrostro] Add comments and license to streaming RateLimiter.scala
7066438 [Issac Buenrostro] Moved throttle code to RateLimiter class, smoother pushing when throttling active
ccafe09 [Issac Buenrostro] Throttle BlockGenerator to limit rate of data consumption.

(cherry picked from commit 2dd67248503306bb08946b1796821e9f9ed4d00e)
Signed-off-by: Tathagata Das <tathagata.das1565@gmail.com>
SPARK-2427: Fix Scala examples that use the wrong command line arguments index

The Scala examples HBaseTest and HdfsTest don't use the correct indexes for the command line arguments. This due to to the fix of JIRA 1565, where these examples were not correctly adapted to the new usage of the submit script.

Author: Artjom-Metro <Artjom-Metro@users.noreply.github.com>
Author: Artjom-Metro <artjom31415@googlemail.com>

Closes #1353 from Artjom-Metro/fix_examples and squashes the following commits:

6111801 [Artjom-Metro] Reduce the default number of iterations
cfaa73c [Artjom-Metro] Fix some examples that use the wrong index to access the command line arguments

(cherry picked from commit ae8ca4dfbacd5a5197fb41722607ad99c190f768)
Signed-off-by: Reynold Xin <rxin@apache.org>
[SPARK-2431][SQL] Refine StringComparison and related codes.

Refine `StringComparison` and related codes as follows:
- `StringComparison` could be similar to `StringRegexExpression` or `CaseConversionExpression`.
- Nullability of `StringRegexExpression` could depend on children's nullabilities.
- Add a case that the like condition includes no wildcard to `LikeSimplification`.

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #1357 from ueshin/issues/SPARK-2431 and squashes the following commits:

77766f5 [Takuya UESHIN] Add a case that the like condition includes no wildcard to LikeSimplification.
b9da9d2 [Takuya UESHIN] Fix nullability of StringRegexExpression.
680bb72 [Takuya UESHIN] Refine StringComparison.

(cherry picked from commit f62c42728990266d5d5099abe241f699189ba025)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-2415] [SQL] RowWriteSupport should handle empty ArrayType correctly.

`RowWriteSupport` doesn't write empty `ArrayType` value, so the read value becomes `null`.
It should write empty `ArrayType` value as it is.

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #1339 from ueshin/issues/SPARK-2415 and squashes the following commits:

32afc87 [Takuya UESHIN] Merge branch 'master' into issues/SPARK-2415
2f05196 [Takuya UESHIN] Fix RowWriteSupport to handle empty ArrayType correctly.

(cherry picked from commit f5abd271292f5c98eb8b1974c1df31d08ed388dd)
Signed-off-by: Michael Armbrust <michael@databricks.com>