[Spark 2060][SQL] Querying JSON Datasets with SQL and DSL in Spark SQL

JIRA: https://issues.apache.org/jira/browse/SPARK-2060
I tried 
```
jsonSchemaRDD.
  where('num_str > BigDecimal("92233720368547758060")).
  select('num_str + 1.2 as Symbol("num"))
```

But, the plan I got is 
```
Project [(CAST(num_str#65:4, DoubleType) + 1.2) AS num#78]
 Filter (CAST(CAST(num_str#65:4, DoubleType), DecimalType) > 92233720368547758060)
  ExistingRdd [num_bool#61,num_num_1#62L,num_num_2#63,num_num_3#64,num_str#65,str_bool#66]
```
Seems we need to take a look at `HiveTypeCoercion`.