Issue #613: save the experiment instances file whenever user joins an experiment
Issue #613 : code refactoring
Issue #613 : save experiment instances when deleting an experiment or cleaning all experiments, and code refactoring accordingly
Issue #613 : store definitions whenever we get the definitions successfully from server, remove the unnecessary storage code.
Issue #613 : code refactoring
Issue #613 : code refactoring of loading definitions from file
Issue #613 : remove legacy code