Add option to show a maximum number of key items

[mjordan]

Where a report shows a very high number of results, it would be useful to allow users to determine how many to show. For example, this output is not very readable:

If the user could indicate they only wanted to see the top 10 results, the chart would be more readable. Or even a range. The CSV should always include all results since it is easy to put into a spreadsheet for manipulation.