TrainingPlan approval messaging (node & researcher side)

Adds Training plan approval New features:

• new message ApprovalRequest/ApprovalReply that sends a model to Node and waits for its approval
• cli: new options for approving and rejecting model
• update list_model method, adding possibility to do queries

issues:

• works different then check_model_status method
• not enough test coverage (only at 69%)
• no cli command for viewing the code
• possible design issue in cli.py (same piece of code repeated several time)
• no option to notify Reasercher if model has been Rejected