Sasctl

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**Bugfixes**
- Added PZMM fitstat JSON file to manifest.

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**Improvements**
- PZMM module moved from a stand-alone [repository](https://github.com/sassoftware/open-model-manager-resources/tree/master/addons/picklezip-mm) to a sasctl submodule.
- Introduced deprecation warnings for Python 2 users.

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**Bugfixes**
- Fixed PyMAS utilities to correctly work functions not bound to pickled objects.
- Model target variables should no longer appear as an input variable when registering ASTORE models.

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**Improvements**
- Registered Python models will now include both `predict` and `predict_proba` methods.
- Added a new Relationships service for managing links between objects.
- Added a new Reports service for retrieving SAS Visual Analytics reports.
- Added a new Report_Images service for rendering content from reports.
- Additional metadata fields are set when registering an ASTORE model.
- Collections of items should now return an instance of `PagedList` for lazy loading of results.
- Module steps can now be called using `module.step(df)` where `df` is the row of a DataFrame or Numpy array.
- `register_model` sets additional project properties when registering an ASTORE model.

**Changes**
- Replaced the `raw` parameter of the `request` methods with a `format` parameter, allowing more control over the
returned value.
- The `get_file_content` method of the Files service now returns the actual content instead of the file metadata.
- JSON output when using `sasctl` from the command line is now formatted correctly.

**Bugfixes**
- `model_publish.delete_destination` now works correctly.

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**Bugfixes**
- Fixed an issue where the `REQUESTS_CA_BUNDLE` environment variable was taking precedence over the `verify_ssl` parameter.

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**Changes**
- Saving of package information can now be disabled using the `record_packages` parameter of `register_model`.

**Bugfixes**
- Added support for uint data types to the `register_model` task.
- Fixed an issue where long package names caused `register_model` to fail.
- `Session` creation now works with older versions of urllib3.