Adding feature for getting source of the class defined in IPython kernel/Notebooks

This merge request contains following changes

• The module common/utils that contains methods to get class source even it is defined in IPython kernel
• Removing %%writefile magic method from all notebooks
• Creating parent BaseTrainingPlan that contains common methods that are defined in training plans
• Moving training plans into directory common/training_plans
• Creating __init__.py in the directory training_plans
• Adding unit tests for common.utils
• Adding unit tests for BaseTrainingPlan
• Update default models saved under envs/default_models/with the new way of importing training plans
• Using is_ipython in expeeriment -> exp_exception instead in_notebook