Move to relational vcf storage and backend queries

This is The Great Migration. 

This PR introduces a schema for and code around loading VCFs into a PostgreSQL database, as well as querying those records via a JSON RESTful API. 

Much work needs to be done to fully integrate this and patch up the code touched by the change (hint: most of it). 

1. Charts and the Karyogram on the examine page.
2. Clean up SQL construction
    1. Remove or update models.py
    2. handle possible injection issues (use SQLAlchemy more here?)
3. Clean up views.py
4. Improve validations.py & associated field names. 
5. Explore: Serialize records and send them to client after initial load. 
6. Performance optimizations.
7. Robust workers.
8. Fix concordance worker & visualization (need a new table in the DB).
9. Fix/remove scorer worker.
10. TESTS!
11. Variant sorting tabs need to be fixed.

And probably some more. Will be adding these as issues.
Pull out this query generation logic, it's duplicated between `get` and `calculate_stats`.

```python
def _form_query(base_query, base_params, functions):
  ...
  return query, params
```