Fix all cloning issues with pyod models

[Yard1]

Signed-off-by: Antoni Baum antoni.baum@protonmail.com

This PR fixes all issues with pyod model cloning by ensuring that scikit-learn API requirements are followed. No logic has been changed. The previously commented out cloning tests have been reenabled and are passing, as well as other tests for the models changed.

Being able to clone models is critical for https://github.com/pycaret/pycaret, which uses pyod's models for its Anomaly Detection module.

All Submissions Basics:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you checked all Issues to tie the PR to a specific one?

All Submissions Cores:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
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• Does your submission pass tests, including CircleCI, Travis CI, and AppVeyor?
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New Model Submissions:

• Have you created a .py in ~/pyod/models/?
• Have you created a _example.py in ~/examples/?
• Have you created a test_.py in ~/pyod/test/?
• Have you lint your code locally prior to submission?

[yzhao062]

Sorry for being extremely late on this. It will be in the latest version today.