Change add_annotations error handling

[tobsecret]

Sometimes a column looks like it's continuous, but fails to convert to float, like e.g. Cigarettes.per.Day which was drawn from a questionnaire which offered 0, 1, 3, 5, ... and the option Unknown. As a result of this, add_annotations will throw an error, saying it cannot convert 'Unkown' to float. This should probably be wrapped in a try/except statement that tells you which columns it had trouble converting. Not entirely sure if it'll be like in the code below, but it's just a sketch for now.

try: 
        self.continuous_annotations = annotations[
            annotations.columns[column_types == 1]
        ].astype(float)
except ValueError:
        for column in annotations.columns[column_types == 1]:
                if not check_column_float_convertible(annotations.loc[:,column]):
                        logging.error(f'{column} column cannot be converted to float, check unique values')
        ValueError("Unable to convert columns to float")