Advanced search form: labels and focus order

[aviannamiller]

Freedom has the same a11y issues with the advanced search form as Lively (as noted in omeka/theme-lively#2):

• None of the fields in the search-narrow-by-fields container are receiving label readouts via screen reader, so it is difficult to discern what text fields and dropdowns are for. It appears they have incorrect aria-labelledby attributes that may be causing this issue.
• There is an illogical focus order after .add-value buttons are activated. Focus stays on the trigger element (the button) and progresses to the next element after tabbing. Instead, focus should move to the newly added element and its appropriate field items.