R1:486f7c1e8e23

Add aggregated facts to the Facts application

Summary:
Some facts are aggregations of other facts. For example, we may compute how many times each macro is used in each object as a "raw fact":

Dnnn uses macro "psyduck" 6 times.

But we want to present this data in aggregate form, e.g. "order macros by popularity". We can do this at runtime and it probably won't be too awful a query, but we can also aggregate it cheaply:

Macro "psyduck" is used 3920 times across all objects.

...and then do a query…