Make a kernel that uses generics

[sdboyer]

Thema's kernels are an ideal place to use generics: Make a kernel with type T; take []byte in, spit T out.

I haven't played enough with generics yet to have a confident vision of exactly what it should look like, but i currently see no reason to believe that we shouldn't just replace the existing InputKernel entirely with this approach.

This is also pretty self-contained - i suspect somebody else could pick it up :)