Improve append_data_to_historic exception handling

[lorae]

The function append_data_to_historic within the HistoricDataComparer class contains a try-except block. The except is specifically a FileNotFoundError, which can introduce issues if the file is found but does not comport to the data standards assumed in the try block.

Create more graceful, generic error handling and a specific version of error handling when the file exists but does not comport with data standards. Once this is complete, remove the print statements (e.g. "existing_df read", "column order mapped", etc).