handle: A Range that handles an Exception

When a Exception occurs inside a range chaining the whole chain dies usually. The Handle range fixes that, as it catches a defined exception and calls an user defined handler on it.
As I mentioned above, this should probably be `T` rather than `E`, but more than that, it needs to ensure that you're dealing with an exception type, so it should be either `E : Exception` or `E : Throwable` (probably the latter) in order to ensure that non-exceptions aren't passed to it. You should probably also consider using multiple layers of templates so that `alias handle!Exception myhandle` can be used. And actually, looking at that, I take back what I said about `handle` being renamed. Since you have to pass the exception type, it's clear enough, and `handleException!Exception` would be kind of ridiculous.