Automated rounding of results in measures

[benbc]

Provide an option to round all numbers in numerators and denominators to the nearest 5. This is another way to avoid the disclosivity of small numbers that may be better than suppression in some cases and can also be implemented automatically.

[LFISHER7]

Our recommendation with measures is now to redact and round them according to the note here. Before we add rounding, we should allow users to specify the redaction threshold (min 5), so that they can meet these recommendations if they are implementing their own rounding having used the in built redaction. Once we add rounding, we can assert that redaction is also set, and that the threshold is min 7.