[SPARK-4041][SQL] Attributes names in table scan should converted to lowercase when compare with relation attributes

In ```MetastoreRelation``` the attributes name is lowercase because of hive using lowercase for fields name, so we should convert attributes name in table scan lowercase in ```indexWhere(_.name == a.name)```.
```neededColumnIDs``` may be not correct if not convert to lowercase.

Author: wangfei <wangfei1@huawei.com>
Author: scwf <wangfei1@huawei.com>

Closes #2884 from scwf/fixColumnIds and squashes the following commits:

6174046 [scwf] use AttributeMap for this issue
dc74a24 [wangfei] use lowerName and add a test case for this issue
3ff3a80 [wangfei] more safer change
294fcb7 [scwf] attributes names in table scan should convert lowercase in neededColumnsIDs
[SQL] Correct a variable name in JavaApplySchemaSuite.applySchemaToJSON

`schemaRDD2` is not tested because `schemaRDD1` is registered again.

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

Closes #2869 from yhuai/JavaApplySchemaSuite and squashes the following commits:

95fe894 [Yin Huai] Correct variable name.