New Interpolators and Orthogonal Spline Collocation

[fedebotu]

Add new interpolators and the Orthogonal Spline Collocation under torchdyn/numerics/interpolators.py. Would be a fine addition to our collection to add a tutorial as well for the interpolators - in preparation for the GraphSplineNets paper :)

@cbhua

[joglekara]

Here are some existing pytorch implementations for the enterprising scientific computing developer to follow

https://github.com/xitorch/xitorch/blob/master/xitorch/interpolate/interp1.py https://github.com/patrick-kidger/torchcde/tree/master/torchcde