deform2: fix inline version RadioChoiceWidget and CheckboxChoiceWidget

This fixes the inline version of the `RadioChoiceWidget` and `CheckboxChoiceWidget` (in the deform2 branch).
Also adds terse documentation about the `inline` attribute of said widgets.

It also changes the markup for the stacked choice displays to match the examples in the bootstrap documentation.
E.g. `<div class="radio"><label>...</label></div>` instead of just `<label class="radio">...</label>`.