IReadOnlyCollection.ToString() as well as debugger display should be more sensible

[Kittyfisto]

Currently, every IReadOnlyCollection implementation displays the string to the create the SQLite table, but that's hardly of use to users. Something different is needed.
Ordinary .NET collections display their count in the debugger, but that might not be feasible as querying the Count() involves a filesystem roundtrip. A possible output might be its interface definition, .i.e. IDictionary<string, int>, etc..