Extend torch.manualSeed(), getRNGState(), and setRNGState()

Although randomkit relies on torch's Mersenne Twister, and thus has no state to speak of for the uniform numbers, the state is still partly used in `randomkit.gauss()` for "dangling gaussians". We need to deal with it in `torch.manualseed()`, `torch.getRNGState()` and `torch.setRNGState()`: wrapping them should do it.