[WIP] Feature/csv to sql natively

When finished, this PR should address #352. New `into` function calls out to to native COPY function of various DBs.  Has optional `if_exists` argument (similar to pandas) to handle three cases: replace, append, and fail

```python
into(sql,csv, if_exists="replace")
```


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Do you mean you'd like to support BOTH terms used by csv dialects AND PostgreSQL?  I may advocate for just one -- probably csv.dialects as we are using those terms throughout the blaze codebase Also, what do you think about warning when flags/parameters are set which can't be acted upon.  For instance, `quotechar` is not supported by sqlite.