Migrate API to v2 database schema

Change SQL queries in the following routes:

* city
* state
* region
* school
* enrollment

Also, change tests to reflect the new schema where appropriate. Specially in the case of cities, the primary key now becomes pk_cod_ibge (city IBGE code) and, therefore, any query that relies on the city id should use this value instead of the old primary key.

Aliases of fields that have different names were added to ensure compatibility with the UI of LDE.

Please refer to the database repository in order to understand how the current schema works. The corresponding ER diagram can be located there.