[SPARK-2234][SQL]Spark SQL basicOperators  add Except operator

Hi all,
I want to submit a Except operator in basicOperators.scala
In SQL case.SQL support two table do except operator.
select * from table1
except
select * from table2
This operator support the substract function .Return an table with the elements from `this` that are not in `other`.This operator should limit the input SparkPlan Seq only has two member.The check will later support
JIRA:https://issues.apache.org/jira/browse/SPARK-2234

Author: Yanjie Gao <gaoyanjie55@163.com>
Author: YanjieGao <396154235@qq.com>
Author: root <root@node4.(none)>
Author: gaoyanjie <gaoyanjie55@163.com>

Closes #1151 from YanjieGao/patch-6 and squashes the following commits:

f19f899 [YanjieGao] add a new blank line in basicoperators.scala
2ff7d73 [YanjieGao] resolve the identation in SqlParser and SparkStrategies
fdb5227 [YanjieGao] Merge remote branch 'upstream/master' into patch-6
9940d19 [YanjieGao] make comment less than 100c
09c7413 [YanjieGao] pr 1151 SqlParser add cache ,basic Operator rename Except and modify comment
b4b5867 [root] Merge remote branch 'upstream/master' into patch-6
b4c3869 [Yanjie Gao] change SparkStrategies Sparkcontext to SqlContext
7e0ec29 [Yanjie Gao] delete multi test
7e7c83f [Yanjie Gao] delete conflict except
b01beb8 [YanjieGao] resolve conflict sparkstrategies and basicOperators
4dc8166 [YanjieGao] resolve conflict
fa68a98 [Yanjie Gao] Update joins.scala
8e6bb00 [Yanjie Gao] delete conflict except
dd9ba5e [Yanjie Gao] Update joins.scala
a0d4e73 [Yanjie Gao] delete skew join
60f5ddd [Yanjie Gao] update less than 100c
0e72233 [Yanjie Gao] update SQLQuerySuite on master branch
7f916b5 [Yanjie Gao] update execution/basicOperators on master branch
a28dece [Yanjie Gao] Update logical/basicOperators on master branch
a639935 [Yanjie Gao] Update SparkStrategies.scala
3bf7def [Yanjie Gao] update SqlParser on master branch
26f833f [Yanjie Gao] update SparkStrategies.scala on master branch
8dd063f [Yanjie Gao] Update logical/basicOperators on master branch
9847dcf [Yanjie Gao] update SqlParser on masterbranch
d6a4604 [Yanjie Gao] Update joins.scala
424c507 [Yanjie Gao] Update joins.scala
7680742 [Yanjie Gao] Update SqlParser.scala
a7193d8 [gaoyanjie] [SPARK-2234][SQL]Spark SQL basicOperators add Except operator #1151
5c8a224 [Yanjie Gao] update the line less than 100c
ee066b3 [Yanjie Gao] Update basicOperators.scala
32a80ab [Yanjie Gao] remove except in HiveQl
cf232eb [Yanjie Gao] update 1comment 2space3 left.out
f1ea3f3 [Yanjie Gao] remove comment
7ea9b91 [Yanjie Gao] remove annotation
7f3d613 [Yanjie Gao] update .map(_.copy())
670a1bb [Yanjie Gao] Update HiveQl.scala
3fe7746 [Yanjie Gao] Update SQLQuerySuite.scala
a36eb0a [Yanjie Gao] Update basicOperators.scala
7859e56 [Yanjie Gao] Update SparkStrategies.scala
052346d [Yanjie Gao] Subtract is conflict with Subtract(e1,e2)
aab3785 [Yanjie Gao] Update SQLQuerySuite.scala
4bf80b1 [Yanjie Gao] update subtract to except
4bdd520 [Yanjie Gao] Update SqlParser.scala
2d4bfbd [Yanjie Gao] Update SQLQuerySuite.scala
0808921 [Yanjie Gao] SQLQuerySuite
a8a1948 [Yanjie Gao] SparkStrategies
1fe96c0 [Yanjie Gao] HiveQl.scala update
3305e40 [Yanjie Gao] SqlParser
7a98c37 [Yanjie Gao] Update basicOperators.scala
cf5b9d0 [Yanjie Gao] Update basicOperators.scala
8945835 [Yanjie Gao] object SkewJoin extends Strategy
2b98962 [Yanjie Gao] Update SqlParser.scala
dd32980 [Yanjie Gao] update1
68815b2 [Yanjie Gao] Reformat the code style
4eb43ec [Yanjie Gao] Update basicOperators.scala
aa06072 [Yanjie Gao] Reformat the code sytle