Add tests for select ops and update numpy+dask Select class

[edoyango]

In addition to adding tests, this "fixes" the numpy and dask Select classes so that they do what is said in the doc string. For example,

from pyearthtools.pipeline.operations.dask.select import Select
import dask.array as da

incoming_data = da.zeros((10,5,2))
select = Select([0])
print(select.apply_func(incoming_data).shape)
select = Select([0, None, 0])
print(select.apply_func(incoming_data).shape)

prints

(10, 5, 1)
(10, 5, 1)

instead of the expected (as per the doc string)

(5,2)
(5)

the old numpy Select does the same thing.

I found the logic difficult to follow, so to correct the behaviour, I rewrote the classes to use numpy/dask's native tuple/slice indexing instead.

The xarray select class does the right thing so didn't need changes.

[coveralls]

Pull Request Test Coverage Report for Build 20802458553

Details

• 107 of 107 (100.0%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.6%) to 65.631%

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Totals
Change from base Build 20305027296:	0.6%
Covered Lines:	10636
Relevant Lines:	15846

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💛 - Coveralls