dripl granularity formatting

* Fixed badly formatted output for rows with missing values
* Changed display of responses where granularity is set

### Before

```console
+-------------------------------+-------+---------+
| timestamp                     | dim   | metric  |
+-------------------------------+-------+---------+
| 2013-12-01T00:00:00.000+01:00 | 0     |
| 2013-12-01T00:00:00.000+01:00 | false | 5905355 |
| 2013-12-01T00:00:00.000+01:00 | true  | 2313231 |
| 2013-12-02T00:00:00.000+01:00 | 0     |
| 2013-12-02T00:00:00.000+01:00 | false | 3493253 |
| 2013-12-02T00:00:00.000+01:00 | true  | 4968431 |
| 2013-12-03T00:00:00.000+01:00 | 0     |
| 2013-12-03T00:00:00.000+01:00 | false | 5849210 |
| 2013-12-03T00:00:00.000+01:00 | true  | 8798012 |
+-------------------------------+-------+---------+
```

### After

```console
+---------------+---------------+
| dim           | metric        |
+---------------+---------------+
| 2013-12-01T00:00:00.000+01:00 |
+---------------+---------------+
|               | 0             |
| false         | 5905355       |
| true          | 2313231       |
+---------------+---------------+
| 2013-12-02T00:00:00.000+01:00 |
+---------------+---------------+
|               | 0             |
| false         | 3493253       |
| true          | 4968431       |
+---------------+---------------+
| 2013-12-03T00:00:00.000+01:00 |
+---------------+---------------+
|               | 0             |
| false         | 5849210       |
| true          | 8798012       |
+---------------+---------------+
```