mitigate squeezing for [integer] selections

[tomsail]

Typically as @jurjendejong mentioned in #56,

ds.isel(time=[0]).Z.data

fails with the following error:

IndexError: too many indices for array: array is 2-dimensional, but 3 were indexed

this is due to the

return data.squeeze()

that is too simple for such selections.

Something needs to be implemented for the following selections types:

ds.isel(time=[0]).Z.data
ds.isel(node=[0]).Z.data
ds.isel(plan=[0]).Z.data

[tomsail]

@jurjendejong

This should be fully fixed now.
Please let me know if the latest main works for you too.

FIY I have tried all sorts of selection types:

import xarray as xr 
import glob
file3 = "tests/data/r3d_bump.slf"
ds = xr.open_dataset(file3)

for selection in [1, [1], [0,1,2], slice(0,1), [0,-1], slice(2,None)]:
    print("selection is ", selection)
    print(ds.isel(time=selection).Z.data.shape)
    print(ds.isel(plan=selection).Z.data.shape)
    print(ds.isel(node=selection).Z.data.shape)

[tomsail]

fixed with #58