[SPARK-15286][SQL] Make the output readable for EXPLAIN CREATE TABLE and DESC EXTENDED

#### What changes were proposed in this pull request?
Before this PR, the output of EXPLAIN of following SQL is like

```SQL
CREATE EXTERNAL TABLE extTable_with_partitions (key INT, value STRING)
PARTITIONED BY (ds STRING, hr STRING)
LOCATION '/private/var/folders/4b/sgmfldk15js406vk7lw5llzw0000gn/T/spark-b39a6185-8981-403b-a4aa-36fb2f4ca8a9'
```
``ExecutedCommand CreateTableCommand CatalogTable(`extTable_with_partitions`,CatalogTableType(EXTERNAL),CatalogStorageFormat(Some(/private/var/folders/4b/sgmfldk15js406vk7lw5llzw0000gn/T/spark-dd234718-e85d-4c5a-8353-8f1834ac0323),Some(org.apache.hadoop.mapred.TextInputFormat),Some(org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat),None,false,Map()),List(CatalogColumn(key,int,true,None), CatalogColumn(value,string,true,None), CatalogColumn(ds,string,true,None), CatalogColumn(hr,string,true,None)),List(ds, hr),List(),List(),-1,,1463026413544,-1,Map(),None,None,None), false``

After this PR, the output is like

```
ExecutedCommand
:  +- CreateTableCommand CatalogTable(
	Table:`extTable_with_partitions`
	Created:Thu Jun 02 21:30:54 PDT 2016
	Last Access:Wed Dec 31 15:59:59 PST 1969
	Type:EXTERNAL
	Schema:[`key` int, `value` string, `ds` string, `hr` string]
	Partition Columns:[`ds`, `hr`]
	Storage(Location:/private/var/folders/4b/sgmfldk15js406vk7lw5llzw0000gn/T/spark-a06083b8-8e88-4d07-9ff0-d6bd8d943ad3, InputFormat:org.apache.hadoop.mapred.TextInputFormat, OutputFormat:org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat)), false
```

This is also applicable to `DESC EXTENDED`. However, this does not have special handling for Data Source Tables. If needed, we need to move the logics of `DDLUtil`. Let me know if we should do it in this PR. Thanks! rxin liancheng

#### How was this patch tested?
Manual testing

Author: gatorsmile <gatorsmile@gmail.com>

Closes #13070 from gatorsmile/betterExplainCatalogTable.