ISL mixed with RFServer

The ISL implementation in RFServer should be properly separated in its own class class that inherits from RFServer. This class would be in a module of its own, becoming an option to the user.

Joe, how hard do you think this would be? I took a quick look at the code, and it seems easy. I can separate it if you want, but I don't have the knowledge to test it...

[joestringer]

I was encouraging @KitL to try to revamp RFServer along this idea, but it turns out that it's not that straightforward. I don't really recall the details, but it seems error-prone particularly if you don't spend the time to sit down and understand how ISL works. As I understand the current ISL code has also changed significantly since this.