Results printed as a ascii table (and added json switch)

Hi,
This is basic implementation of results formated as ascii table:

```
| key                | types        | occurrences | percents |
| ------------------ | ------------ | ----------- | -------- |
| _id                | ObjectId     | 5           | 100      |
| name               | String       | 5           | 100      |
| bio                | String       | 3           | 60       |
| pets               | String,Array | 2           | 40       |
| birthday           | String       | 2           | 40       |
| someBinData        | BinData-old  | 1           | 20       |
| someWeirdLegacyKey | String       | 1           | 20       |
```

Could you please review the code? 

Ascii format is the default. There is optional ```outputFormat=json``` switch. Next step should be to provide possibility to mute all the debug output and print only valid JSON.