Make the default trending smarter

When you switch from rank to trend, the report always defaults to "day" and you have to then change it.

If my timeframe was 30 days, that's fine. But if my timeframe was 12 months, do months, if it was 52 weeks, do weeks. If it was 59 days, then I suppose days would still be the default; in short, save me the obvious step by setting the level to the nearest large-block-division of the selected timeframe.