* Support returning the correct values for the different QuerySet methods when using .values() and .values_list().
* Fix slicing on QuerySet. Fix django queries test, and remove some ignored errors that are no longer needed.
* Remove accidental change in RawQuerySet.
* Readded some still-necessary ignores to aggregation django test.
* Add more tests of first/last/earliest/last/__getitem__, per mkurnikov's comments.
- Fix .iterator()
* Re-add Iterator as base-class of QuerySet.
* Make QuerySet a Collection.
* - Fix return type for QuerySet.select_for_update().
- Use correct return type for QuerySet.dates() / QuerySet.datetimes().
- Use correct type params in return type for QuerySet.__and__ / QuerySet.__or__
- Re-add Sized as base class for QuerySet.
- Add test of .all() for all _Row types.
- Add test of .get() for all _Row types.
- Remove some redundant QuerySet method tests.
* Automatically fill in second type parameter for QuerySet.
... if second parameter is omitted.
* Fix bug where models with a class variable using a manager defined would interfere with other managers.
- Fill in the type argument for that particular instance of the manager, rather than modifying the bases of the Manager type.
- Instantiate a new Instance from determine_proper_manager_type so The code doesn't crash under mypy-mypyc.
* Use helpers.reparametrize_instance per review comment.
* Updated ignored errors in Django test for get_objects_or_404.
- For some reason, `Manager[nothing]` is now removed from expected types.
However, I think this makes sense anyway, as Manager is a subclass of QuerySet.
* Make CharField(blank=True) not be considered nullable
The documentation on [blank](https://docs.djangoproject.com/en/2.1/ref/models/fields/#blank) says that it "will allow the entry of an empty value", which for a string is just a 0-length string. This patch allows `CharField(blank=True,...)` to no longer be considered `Optional`.
closes#38
* fixed tests for `CharField(blank=True)`
* allow blank CharField to be nullable in the constructor, but the underlying type
is str (unless `null=True`)
- Made id_list of type Sequence[Any], rather than Any, according to mkurnikov's review.
- Removed **kwargs.
- Made returned Dict keys of type Any rather than int or str as it depends on the provided field's type.
- Added test with examples from Django docs.
- The keys are still Union[int, str] which doesn't cover all
possibilities, but it's not possible to cover without handling this in
the plugin, because the type of the Dict keys are dynamic depending on
which value for field_name you pass in.
