inconsistent slicing with one element.

[grst]

When slicing AnnData with a List of one (adata[:, [0]]) element, I expect it to return a 2d array.
When slicing AnnData with one element (adata[:, 0]), I expect it to return a 1d array.
AnnData always returns a 1d array.

See the following example

a = np.ones((3, 3))
adata = AnnData(a)

Expected behaviour (like in numpy)

> a[:, [0]]
array([1., 1., 1.])
> a[:, 0]
array([[1.],
       [1.],
       [1.]])
> adata.X[:, [0]]
array([[1.],
       [1.],
       [1.]], dtype=float32)

Actual behaviour:

> adata[:, 0].X
ArrayView([1., 1., 1.], dtype=float32)
> adata[:, [0]].X

This is somewhat related to #60. I still opened a separate issue as in my case the behavious is actually inconsistent with numpy.

[falexwolf]

Right! This should be fixed! Thank you for pointing this out! I'll do that soon!

[ivirshup]

We've gone with behavior more like an ExpressionSet than a numpy array, but we decided on a consistent solution. Closed by #164.