[Accessibility] - Group ticket

[transkamp]

the following accessibility problems exist

1. Contrast problem in autocomplete list (autumn theme)
   

2. "Delete" button is not focusable in keyboard navigation
   

3. Dropdown lists are not rendered correctly in the screen reader (NVDA). The selected element is rendered as empty.
   

4. label and legend elements are missing in the form fields
   
   more infos: https://accessibility.blog.gov.uk/2016/07/22/using-the-fieldset-and-legend-elements/

[sholtkamp]

3. & 4. Have been implemented into the Bundle.
4. & 2. Cannot be included as of now due to technical limitations.