need a version of G-Jones that's delay/delay rate

[o-smirnov]

For some applications, we want a (scalar) G-Jones that is parameterized as

G(t,\nu) = exp{-i_(\phi_0 + a_t + b*\nu)}

where each antenna has its own \phi_0, a, b parameters.

Of course we can currently just compute this on the CPU, but it would be a lot faster if we could just pass in three numbers per antenna.

Not urgent @sjperkins, just throwing it out there to get initial thoughts.

[sjperkins]

@o-smirnov This certainly viable. I think the challenge here is to make the montblanc pipeline plug and playable. This will require some thought about slotting different operations at different phases of the pipeline. Created an umbrella issue #168.