save fluff documents directly to SQL

Gives you the option of saving fluff data directly to SQL (bypassing couchdb altogether). Table structure is compatible with existing `ctable` tables (besides table name change and one additional column).

Enabled by setting `save_direct_to_sql=True` in Fluff indicator doc:

```
class MyIndicators(fluff.IndicatorDocument):
    save_direct_to_sql = True
    ....
```