New Playground Workflow

[hp2500]

Added various methods to ModelPlayground

• activate(): sets up live playground page without comeptetion/experiment
• create(): sets up live playground page with competition/experiment
• submit_model(): allows to submit directly to playground, defaults to experiment
• update_example_data(): allows to submit example data after playground is created
• update_labels(): allows to submit y_train for classification models after playground is created
• various other methods previously associated with competitions / experiments now work for playgrounds
• model objects / preprocessor functions can be passed directly (I think we merged this into master earlier, but it is not yet reflected in tutorials)
• Backward compatibility should be ensured, but lets test this thoroughly
• Also prepared 3 test notebooks for sklearn, keras, pytorch that I will circulate on slack