DataManager class introduction

[debpal]

• Introduced a DataManager class to generate simulated time series DataFrame
• Made target_dir an optional parameter with default value None in the run_swat function
• Updated print_prt_control configuration in _apply_swat_configuration to prevent setting None as obj and allow empty dictionaries for time frequency
• Added explicit return None statements in several functions in utils.py and validators.py for consistency
• Removed the TxtInOut test data folder from the .gitignore file