Generalize and specialize my calculate function.

This routes the `RichObservable.map` through my `calculate` and adds
predefined `calculate` signatures for 1, 2, 3 or 4 arguments. (This way,
in most normal cases you won't have to explicitly specify the types of
the arguments in your function.) They all go through the same inner
code, so we have unified logging, subscription rules, etc.
Reduce default Lanczos lobes to two.

I tend to think this looks better than three-lobe Lanczos.
Logging message.