Category.tags should have count restriction parameters

[fluffy-critter]

Expected Behavior

It should be possible to restrict the category.tags list based on the number of entries which have them; for example:

• min_count=2 to only show tags which apply to at least two entries
• max_count to limit to ones below a certain threshold
• something to limit tags to only a certain percentile rank, for example count_percentile=(5,95) to only show tags which occur in at least 5% of entries but no more than 95% of them (to filter out tags which appear for everything in a category, for example)