Definite SQLAlchemy naming conventions

[heartsucker]

For reference: https://docs.sqlalchemy.org/en/latest/core/constraints.html#configuring-constraint-naming-conventions

We should use the recommended standard:

convention = {
  "ix": 'ix_%(column_0_label)s',
  "uq": "uq_%(table_name)s_%(column_0_name)s",
  "ck": "ck_%(table_name)s_%(constraint_name)s",
  "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
  "pk": "pk_%(table_name)s"
}

metadata = MetaData(naming_convention=convention)

This will save us from problems later when dealing with indexes and constraints.