Parsing

Included some code from my first pyslk parser, just a draft request for now...

• _parse_list_to_rows: added new parsing algorithm that parses the command line output before making a dataframe
• _rows_to_dataframe: creates dataframe from the result of _parse_list_to_rows
• _parse_sizes: parses filesize in slk format to integer bytes

This two step approach allows for also parsing recursive list results.