Make the interpolators dask-compatible

[mraspaud]

Problem description

At the moment, most of the interpolator aren't dask-friendly, which in turn necessitates a lots of workarounds in the code using geotiepoints.

This is a feature request to make geotiepoints as dask-compatible as possible. Supporting xarray.DataArrays would also be nice.

[djhoese]

I forgot this issue existed. My work in #38 added a scanline_mapblocks decorator that automatically extracts dask arrays and runs the interpolations with dask's map_blocks. It also supports xarray DataArrays.