Make default methods for capsule items

[shunichironomura]

• Update GitRepositoryContext default method parameters
• add default method to GitRepositoryContext
• Use default for JsonDumpReporter in example
• add default method to FileContext
• Use default methods
• add check argument to CommandContext
• add the base case for the default method
• add contexts and watchers
• Add project root search function in utils.py
• Add default run directory generator to run decorator
• Add run_dir attribute in Run class
• Add 'current_run_dir' function to capsula module
• Simplify decorator and add current run dir log
• Refactor capsula to use current_run_name instead of current_run_dir
• Update logger info in decorator.py