- A change in the ordering when columns and constraints are dropped;
autogenerate will now place the "drop constraint" calls *before*
the "drop column" calls, so that columns involved in those constraints
still exist when the constraint is dropped.
fixes #247
include indexes in batch
- Added a rule for Postgresql to not render a "drop unique" and "drop index"
given the same name; for now it is assumed that the "index" is the
implicit one Postgreql generates.   Future integration with
new SQLAlchemy 1.0 features will improve this to be more
resilient.
fixes #247