Codebase Improvements

[debpal]

• Changed input date type in set_begin_and_end_date from datetime.date to string for user convenience
• Removed redundant error statements that were either unnecessary or dependent on others
• Removed the register_file method as it was not required
• Standardized quotes by replacing double quotes with single quotes where appropriate
• Shortened some function names in TxtinoutReader class
• Renamed function names in validators.py starting with _calibration for consistency
• Made minor modifications in utils.py