New convenience constructors

Hi!
I would like to add some new convenience copnstructors and would create a new PR if that was supposed to be a good idea and something that should be part of this package.

What I mean here is the following:
The command `linear_interpolation(x, y)` is for example a shortcut for `extrapolate(interpolate((x, ), y, Gridded(Linear())), Throw())`. In the same way I would, for example for the recently created `AkimaMotonicInterpolation` type, make it possible to call `akima_spline(x, y)` as a shortcut for `extrapolate(interpolate(x, y, AkimaMontonicInterpolation()), Throw())`.

What are your thoughts on this idea?