Figure out time duration

@sylvia.biscoveanu pointed out yesterday that we can set the segment duration for CBC signals using the method I mentioned in https://git.ligo.org/Monash/tupak/issues/53. I think we should look to implement this for injections pretty soon.

I guess we could just call lalsimulation.SimInspiralChirpTimeBound(fmin, m1, m2, S1, S2) in interferometer.inject_signal and then if the signal doesn't fit in the interferometer's time duration we can extend the time duration with BIG WARNINGS that we're changing the interferometer data.

This will need some care in how the data is reset.

Thoughts?