Add cli show columns command to describe tables

[jimexist]

Which issue does this PR close?

Closes #1232

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

> \?
+---------+---------------------+
| Command | Description         |
+---------+---------------------+
| \d      | list tables         |
| \d name | describe table      |
| \q      | quit datafusion-cli |
| \?      | help                |
+---------+---------------------+
4 rows in set. Query took 0.001 seconds.

> \d
+---------------+--------------------+------------+------------+
| table_catalog | table_schema       | table_name | table_type |
+---------------+--------------------+------------+------------+
| datafusion    | information_schema | tables     | VIEW       |
| datafusion    | information_schema | columns    | VIEW       |
+---------------+--------------------+------------+------------+
2 rows in set. Query took 0.005 seconds.

> \d information_schema.tables
0 rows in set. Query took 0.005 seconds.