In the case of multiple-table inheritance models, get_all_related_objects() and
get_all_related_objects_with_model() don't return the auto-created
OneToOneField, but the new examples didn't account for this.

alter_index_together and alter_unique_together no more use _remake_table method in sqlite3

Factor method signatures in test_autodetector to avoid clashing keyword
arguments when introducing indexes.

Complement to debf521d.

Also removed try/except/fail antipattern that hides exceptions.

Refactored "Prevented unneeded index creation on MySQL-InnoDB" (2ceb10f3)
to avoid setting db_index=False.

Thanks Berker Peksag for the suggestion.

Added the AddIndex and RemoveIndex operations to use them in migrations.

Thanks markush, mjtamlyn, timgraham, and charettes for review and advice.