[SPARK-14476][SQL] Improve the physical plan visualization by adding meta info...

[SPARK-14476][SQL] Improve the physical plan visualization by adding meta info like table name and file path for data source.

## What changes were proposed in this pull request?
Improve the physical plan visualization by adding meta info like table name and file path for data source.

Meta info InputPaths and TableName are newly added. Example:
```
scala> spark.range(10).write.saveAsTable("tt")
scala> spark.sql("select * from tt").explain()
== Physical Plan ==
WholeStageCodegen
:  +- BatchedScan HadoopFiles[id#13L] Format: ParquetFormat, InputPaths: file:/home/xzhong10/spark-linux/assembly/spark-warehouse/tt, PushedFilters: [], ReadSchema: struct<id:bigint>, TableName: default.tt
```

## How was this patch tested?

manual tests.

Changes for UI:
Before:
![ui_before_change](https://cloud.githubusercontent.com/assets/2595532/15064559/3d423e3c-1388-11e6-8099-7803ef496c4d.jpg)

After:
![fix_long_string](https://cloud.githubusercontent.com/assets/2595532/15133566/8ad09e26-1696-11e6-939c-99b908249b9d.jpg)

![for_load](https://cloud.githubusercontent.com/assets/2595532/15157224/3ba95c98-171d-11e6-885a-de0ee8dec27c.jpg)

Author: Sean Zhong <clockfly@gmail.com>

Closes #12947 from clockfly/spark-14476.