[SPARK-2339][SQL] SQL parser in sql-core is case sensitive, but a table alias is converted to lower case when we create Subquery

Reported by http://apache-spark-user-list.1001560.n3.nabble.com/Spark-SQL-Join-throws-exception-td8599.html
After we get the table from the catalog, because the table has an alias, we will temporarily insert a Subquery. Then, we convert the table alias to lower case no matter if the parser is case sensitive or not.
To see the issue ...
```
val sqlContext = new org.apache.spark.sql.SQLContext(sc)
import sqlContext.createSchemaRDD

case class Person(name: String, age: Int)

val people = sc.textFile("examples/src/main/resources/people.txt").map(_.split(",")).map(p => Person(p(0), p(1).trim.toInt))
people.registerAsTable("people")

sqlContext.sql("select PEOPLE.name from people PEOPLE")
```
The plan is ...
```
== Query Plan ==
Project ['PEOPLE.name]
 ExistingRdd [name#0,age#1], MapPartitionsRDD[4] at mapPartitions at basicOperators.scala:176
```
You can find that `PEOPLE.name` is not resolved.

This PR introduces three changes.
1.  If a table has an alias, the catalog will not lowercase the alias. If a lowercase alias is needed, the analyzer will do the work.
2.  A catalog has a new val caseSensitive that indicates if this catalog is case sensitive or not. For example, a SimpleCatalog is case sensitive, but
3.  Corresponding unit tests.
With this PR, case sensitivity of database names and table names is handled by the catalog. Case sensitivity of other identifiers are handled by the analyzer.

JIRA: https://issues.apache.org/jira/browse/SPARK-2339

Author: Yin Huai <huai@cse.ohio-state.edu>

Closes #1317 from yhuai/SPARK-2339 and squashes the following commits:

12d8006 [Yin Huai] Handling case sensitivity correctly. This patch introduces three changes. 1. If a table has an alias, the catalog will not lowercase the alias. If a lowercase alias is needed, the analyzer will do the work. 2. A catalog has a new val caseSensitive that indicates if this catalog is case sensitive or not. For example, a SimpleCatalog is case sensitive, but 3. Corresponding unit tests. With this patch, case sensitivity of database names and table names is handled by the catalog. Case sensitivity of other identifiers is handled by the analyzer.
[SPARK-2386] [SQL] RowWriteSupport should use the exact types to cast.

When execute `saveAsParquetFile` with non-primitive type, `RowWriteSupport` uses wrong type `Int` for `ByteType` and `ShortType`.

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

Closes #1315 from ueshin/issues/SPARK-2386 and squashes the following commits:

20d89ec [Takuya UESHIN] Use None instead of null.
bd88741 [Takuya UESHIN] Add a test.
323d1d2 [Takuya UESHIN] Modify RowWriteSupport to use the exact types to cast.
[SPARK-2375][SQL] JSON schema inference may not resolve type conflicts correctly for a field inside an array of structs

For example, for
```
{"array": [{"field":214748364700}, {"field":1}]}
```
the type of field is resolved as IntType. While, for
```
{"array": [{"field":1}, {"field":214748364700}]}
```
the type of field is resolved as LongType.

JIRA: https://issues.apache.org/jira/browse/SPARK-2375

Author: Yin Huai <huaiyin.thu@gmail.com>

Closes #1308 from yhuai/SPARK-2375 and squashes the following commits:

3e2e312 [Yin Huai] Update unit test.
1b2ff9f [Yin Huai] Merge remote-tracking branch 'upstream/master' into SPARK-2375
10794eb [Yin Huai] Correctly resolve the type of a field inside an array of structs.
[SPARK-2376][SQL] Selecting list values inside nested JSON objects raises java.lang.IllegalArgumentException

JIRA: https://issues.apache.org/jira/browse/SPARK-2376

Author: Yin Huai <huai@cse.ohio-state.edu>

Closes #1320 from yhuai/SPARK-2376 and squashes the following commits:

0107417 [Yin Huai] Merge remote-tracking branch 'upstream/master' into SPARK-2376
480803d [Yin Huai] Correctly handling JSON arrays in PySpark.
[SPARK-2235][SQL]Spark SQL basicOperator add Intersect operator

Hi all,
I want to submit a basic operator Intersect
For example , in sql case
select * from table1
intersect
select * from table2
So ,i want use this operator support this function in Spark SQL
This operator will return the  the intersection of SparkPlan child table RDD .
JIRA:https://issues.apache.org/jira/browse/SPARK-2235

Author: Yanjie Gao <gaoyanjie55@163.com>
Author: YanjieGao <396154235@qq.com>

Closes #1150 from YanjieGao/patch-5 and squashes the following commits:

4629afe [YanjieGao] reformat the code
bdc2ac0 [YanjieGao] reformat the code as Michael's suggestion
3b29ad6 [YanjieGao] Merge remote branch 'upstream/master' into patch-5
1cfbfe6 [YanjieGao] refomat some files
ea78f33 [YanjieGao] resolve conflict and add annotation on basicOperator and remove HiveQl
0c7cca5 [YanjieGao] modify format problem
a802ca8 [YanjieGao] Merge remote branch 'upstream/master' into patch-5
5e374c7 [YanjieGao] resolve conflict in SparkStrategies and basicOperator
f7961f6 [Yanjie Gao] update the line less than
bdc4a05 [Yanjie Gao] Update basicOperators.scala
0b49837 [Yanjie Gao] delete the annotation
f1288b4 [Yanjie Gao] delete annotation
e2b64be [Yanjie Gao] Update basicOperators.scala
4dd453e [Yanjie Gao] Update SQLQuerySuite.scala
790765d [Yanjie Gao] Update SparkStrategies.scala
ac73e60 [Yanjie Gao] Update basicOperators.scala
d4ac5e5 [Yanjie Gao] Update HiveQl.scala
61e88e7 [Yanjie Gao] Update SqlParser.scala
469f099 [Yanjie Gao] Update basicOperators.scala
e5bff61 [Yanjie Gao] Spark SQL basicOperator add Intersect operator