Clumsy columns in facetapi_facet_display_form()

facetapi_facet_display_form() uses floats with 30% width to split form elements across 3 columns.

As a result, the order of elements is kinda random.
And other modules like facetapi_pretty_paths or facetapi_alias have problems placing their own form elements.
See e.g. #2629206: Title and field in admin UI for Pretty path alias are apart

Ideas:
- Using actual CSS columns with column-count: 3.
- Wrapping the elements of each column in a container, and then floating this container, instead of each item separately.

Note that form elements can be nested without changing the name of each element, by setting the #parents explicitly, e.g. '#parents' => array('global').