Cascade delete issues with Overhead

[nvernooy]

Overheads are not deleted when its Project is deleted.

I added a "cascade='all'" to the Overheads relationship in Projects.

But then deleting a Project caused a SQLAlchemy error:

StaleDataError: DELETE statement on table many to many

I'm assuming from the many-to-many relationship between Overheads and BudgetItems.

Using the solution here: http://stackoverflow.com/questions/28824401/sqlalchemy-attempting-to-twice-delete-many-to-many-secondary-relationship
And adding
engine.dialect.supports_sane_rowcount = engine.dialect.supports_sane_multi_rowcount = False
to init.py fixed the error.

Keeping this issue open in case there are any side effects.