Add support for parent + child relationship SOQL queries

**See Pull Request #7 first for background and info about parent relationship query support**

This change supersedes Pull Request #7 for just parent relationship queries and adds supports for child relationship queries as well. Similar to parent relationship queries, child relationships are returned as nested results; however, instead of being nested sobjects, they are nested query results and are best displayed as nested tables. For example:

```
force select "id, name, (select id, name, createdby.name from contacts) from account where id in (select accountid from contact) limit 2"
 Id                 | Name   | Contacts
--------------------+--------+--------------------------------------------------------
 0016000000K7NdWAAV | Google |  Id                 | Name        | CreatedBy.Name
                    |        | --------------------+-------------+----------------
                    |        |  0036000000q0ab9AAA | Larry Page  | Ryan Brainard
                    |        |  0036000000pXGQjAAO | Sergey Brin | Ryan Brainard
                    |        | --------------------+-------------+----------------
                    |        |  (2 records)
                    |        |
 0016000000Khr6YAAR | Yahoo! |  Id                 | Name          | CreatedBy.Name
                    |        | --------------------+---------------+----------------
                    |        |  0036000000qCwxyAAC | Marissa Mayer | Ryan Brainard
                    |        | --------------------+---------------+----------------
                    |        |  (1 records)
                    |        |
--------------------+--------+--------------------------------------------------------
 (2 records)
```

Note in the example that this also supports child relationships looking back up to parent relationships with the display of `Contacts.CreatedBy.Name`.