Update screenshots and description for list-nolabel

http://docs.opendatakit.org/form-widgets/#field-list

The look and feel of label/list-nolabel/list appearances for select_one/select_multiple were changed in v1.8.0 in a way that didn't match their original intended usage.

This was reported at https://forum.opendatakit.org/t/new-list-nolabel-appearance/9255 and fixed for v1.10.0.

The idea with these widgets is that they can be used to build a grid of questions. The form attached on the forum post illustrates that well.

I think it would be useful to mention that this is the intended use and to describe the behavior. Specifically, labels and hints take up half of the screen and choices take up the other half. Some tricks for using it are to establish a legend at the top so the labels are short, to target larger screens and use `
` tags to break up the labels and hints where desired.

Start at the field-list documentation page linked in the issue and review the forum post and attached form for the intended list-nolabel behavior. Update the screenshots and description to explain the v1.10.0 layout, grid-of-questions use, legends, larger screens, and
breaks; done when the page accurately reflects that behavior.

Written by the indexing model from the issue text.