aggregate dependencies at the class level

[SethTisue]

customer feedback seems to be that the most useful level for tracking dependencies is the class — as opposed to a higher level (by package, by source file) or a lower level (by method)

We will need to write new code to aggregate dependencies at the class level. (Version 0.1.2 produces detailed dependency information but does not aggregate it in any way.)

We should:

• Generate a full report showing all of the aggregated dependencies
• Make the aggregated information queryable in the REPL, so e.g. if class C is of interest, we should be able to ask for C’s incoming dependencies and outgoing dependencies