Bugfixes

I have also a few bugfixes and tests that would be good to be added to a bugfix release.

The new test `tests/inspectdb/test.sh` can be run only manually because it tries to create models for all objects, read one record from all of them and to write the same record back. It is slow. It can fail on some your custom object if you have not enough permission for some fields. All known problematic standard object are excluded from that test.