Make hdfeos_l1b geo interpolation use dask arrays

[wroberts4]

Is your feature request related to a problem? Please describe.
_interpolate under satpy.readers.hdfeos_l1b could be more efficient if arrays were converted to be lazy.

Describe the solution you'd like
Convert numpy arrays to dask arrays. This will allow the arrays to be "lazy".

Code to be improved

satpy/satpy/readers/hdfeos_l1b.py

Lines 227 to 276 in 0f7ebef

	def _interpolate(data, coarse_resolution, resolution, interpolator=None):
	if resolution == coarse_resolution:
	return data
	if interpolator is None:
	from geotiepoints.interpolator import Interpolator
	interpolator = Interpolator
	logger.debug("Interpolating from " + str(coarse_resolution)
	+ " to " + str(resolution))
	if isinstance(data, (tuple, list, set)):
	lines = data[0].shape[0]
	else:
	lines = data.shape[0]
	if coarse_resolution == 5000:
	coarse_cols = np.arange(2, 1354, 5)
	lines *= 5
	coarse_rows = np.arange(2, lines, 5)
	elif coarse_resolution == 1000:
	coarse_cols = np.arange(1354)
	coarse_rows = np.arange(lines)
	if resolution == 1000:
	fine_cols = np.arange(1354)
	fine_rows = np.arange(lines)
	chunk_size = 10
	elif resolution == 500:
	fine_cols = np.arange(1354 * 2) / 2.0
	fine_rows = (np.arange(lines * 2) - 0.5) / 2.0
	chunk_size = 20
	elif resolution == 250:
	fine_cols = np.arange(1354 * 4) / 4.0
	fine_rows = (np.arange(lines * 4) - 1.5) / 4.0
	chunk_size = 40
	along_track_order = 1
	cross_track_order = 3
	satint = interpolator(data,
	(coarse_rows, coarse_cols),
	(fine_rows, fine_cols),
	along_track_order,
	cross_track_order,
	chunk_size=chunk_size)
	satint.fill_borders("y", "x")
	return satint.interpolate()

Additional context
@djhoese suggested this improvement.

[djhoese]

@wroberts4 your issue doesn't reference what reader this is for. It would also be helpful if you could point to the specific range of lines or the file where this interpolation is started. Please update the issue to include this information including modifying the title. Thanks.

[djhoese]

@mraspaud You fixed this in 0.10 (can't find the PR right now) didn't you?

[mraspaud]

Well, I didn't fix that code, but switch to the new interpolation we implemented in #430 for Modis makes it dask and xarray friendly.

[mraspaud]

This has been implemented.