Add some more details and explanation to the sample notebooks

[fjug]

Especially for the section where we load data we often see people struggling to understand what dimensions in what order to put there. Even if they use Fiji, they still need to know to invert order.
Then, after loading, we show the shape of the loaded data and it confuses because we shuffle dimensions around (and add one).

Suggestion: add additional cells and text that first discovers what axis order to use, then some more text that describes why after loading it is changed.

Thanks!