Feature/983 data importer

# Warning

# Info

The release includes the new NPSP Data Importer, which helps you easily import your data into the Nonprofit Starter Pack

# Issues

Fixes #983 
Fixes #1020 
Fixes #1015 
Fixes #1014 


For user errors (like specifying an invalid donation donor), I flag the DI record with the failure, but let the rest of the DI's save.  this is why you can end up with successfully running the batch, but some records that get marked as failures.

If I hit a system exception, which is really for unknown reasons since I handle the cases I think the user can run into, I have no choice but to rollback that batch, and mark all the DI records in the batch with the exception.